design of aluminium structures introduction to eurocode 9 ......design of aluminium structures...

Design of aluminium structures

Introduction to Eurocode 9 with worked examples

November 2020





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Table of Contents Chapter 1 - Introduction .................................................................................................................................................... 5

Chapter 2 - History of Aluminium Structures .................................................................................................................... 6

Chapter 3 - Industrial production Process ........................................................................................................................ 9

3.1 Hardening of aluminium ......................................................................................................................................... 9

3.2 Strain hardening .................................................................................................................................................... 10

3.3 Precipitation hardening ......................................................................................................................................... 10

3.4 Artificial ageing ...................................................................................................................................................... 10

3.5 Influence of Heat ................................................................................................................................................... 11

3.6 Alloys ..................................................................................................................................................................... 12

3.6.1 Designation of wrought alloys ........................................................................................................................ 12

3.6.2 Designation of casting alloys .......................................................................................................................... 13

3.7. Tempers and designation of tempers .............................................................................................................. 14

3.7.1 Tempers of non-heat-treatable alloys............................................................................................................ 14

3.7.2 Tempers of heat-treatable alloys ................................................................................................................... 14

3.8 Alloys and tempers of alloys listed in the Eurocode 9 .......................................................................................... 15

3.9 Practical viewpoints for the selection of materials ............................................................................................... 16

3.9.1 Sheet and plate .............................................................................................................................................. 16

3.9.2 Extrusions ....................................................................................................................................................... 16

3.9.3 Castings and forgings ..................................................................................................................................... 17

Chapter 4 - Why Aluminium in Structural Engineering ................................................................................................... 18

4.1 Basic prerequisites ................................................................................................................................................ 18

4.2 Fields of application .............................................................................................................................................. 21

Chapter 5 - Design of aluminium structures according to Eurocode 9 ........................................................................... 24

5.1 Introduction .................................................................................................................................................... 24

Part 1-1 General structural rules ............................................................................................................................. 24

Part 1-2: Structural fire design ................................................................................................................................ 24

Part 1-3: Structures susceptible to fatigue.............................................................................................................. 24

Part 1-4: Cold-formed structures ............................................................................................................................ 25

Part 1-5: Shell structures ......................................................................................................................................... 25

5.2. Main aspects to consider when designing aluminium structures ................................................................... 25

5.3. Limit state design ............................................................................................................................................ 28

5.4. Serviceability limit state .................................................................................................................................. 29



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5.5. Ultimate limit state method ............................................................................................................................ 30

5.6. Ultimate limit state for members.................................................................................................................... 31

5.6.1 General .......................................................................................................................................................... 31

5.6.2 Cross-section class ......................................................................................................................................... 31

5.6.3 Material Buckling Class (BC) and buckling curves ........................................................................................ 32

5.6.4 Effective thickness due to local buckling and HAZ softening ....................................................................... 33

5.6.5 Bending and axial compression .................................................................................................................... 33

5.6.6 Overview of the main design provisions in EN 1999 .................................................................................... 36

Chapter 6 – Examples of applications by using Eurocode 9 ............................................................................................ 55

Example 1: Vertical deflection and resistance of a simply supported beam .............................................................. 55

Example 2: Bending moment resistance of a class 4 cross-section ............................................................................ 57

Example 3: Bending moment resistance of a welded member with a transverse weld ............................................. 59

Example 4: Lateral-torsional buckling of member in bi-axes bending and compression ........................................... 62

Example 5: Welded connection between diagonal and chord member .................................................................... 68

Example 6: Resistance of equivalent T-stub ............................................................................................................... 69

Chapter 7 – Execution of aluminium structures ............................................................................................................. 72

Chapter 8 - Maintenance ................................................................................................................................................ 74

Chapter 9 – Sustainability of aluminium structures ........................................................................................................ 76

9.1.The aluminium cycle ............................................................................................................................................. 76

9.2. Metal sourcing ...................................................................................................................................................... 76

9.3. Transformation ..................................................................................................................................................... 77

9.4. Use phase ............................................................................................................................................................. 77

9.5. Deconstruction and collection ............................................................................................................................. 77

9.6 Recycling ................................................................................................................................................................ 77

Chapter 10 - Applied examples of Aluminium Structures ............................................................................................... 78

10.1. Lattice space structures ..................................................................................................................................... 78

10.2 Reticulated domes .............................................................................................................................................. 78

10.3 Geodetic domes .................................................................................................................................................. 79

10.4 Special structures ................................................................................................................................................ 79

10.5 Off-shore applications ......................................................................................................................................... 80

10.6 Bridges ................................................................................................................................................................. 80

10.7 Architectural buildings ........................................................................................................................................ 81

10.8 Other applications ............................................................................................................................................... 81



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Terms and definitions...................................................................................................................................................... 98

Standards & Normative references ............................................................................................................................... 100

Basic references ............................................................................................................................................................ 102

Other references ........................................................................................................................................................... 102



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Chapter 1 - Introduction

Aluminium is a material of choice for structural application, i.e. for parts contributing to the mechanical resistance and

stability of buildings, constructions, engineering works and transport applications. Roofs for sport arenas, industrial

halls, silos, bridges, trains, ships and oil platforms are just a few examples of where aluminium structures can be found.

To help consumers in getting reliable, consistent and improved product experience, European Aluminium is heavily

involved in the development of standards at both international and European level. On top of more than 120 European

standards for aluminium and its alloys in various forms, which have already been published by the European

Committee for Standardization (CEN) with the support of the aluminium industry, many other standards offer solutions

for the use of aluminium in various sectors.

When looking at structural design for aluminium, Eurocode 9: Design of aluminium structures (often abbreviated as

EN 1999 or EC 9) describes the principles and requirements for the proper design of aluminium alloy structures. While

in general standardisation supports customer’s choices, Eurocode 9 is an excellent tool not only to facilitate customer’s

choices for aluminium products, but also serves as a promotion tool for using aluminium in structures.

This publication is a compendium of basic information on such aspects of aluminium including:

- The reasons to use aluminium for structural purposes

- The description of main aluminium alloys available for structural use

- The design of joints

- Worked examples on the application of Eurocode 9

- Sustainability of aluminium

Developed by European Aluminium with the contributions of Prof. Dr. Ing. Federico Mazzolani, Chairman of CEN

Technical Committee (TC) 250 Sub-Committee (SC) 9 on Eurocode 9: Design of aluminium structures, Prof. Dr. Ing.

Torsten Höglund (Convenor of the TC 250 SC 9 Working Groups for all Parts of Eurocode 9), Dipl. Ing. Reinhold Gitter

and Dipl. Ing. Werner Mader (German representatives in CEN TC 250 SC 9), this document will be of particular interest

to structural engineers designing infrastructures, means of transport, offshore constructions and, more generally, to

anyone with an interest in the applications and development of aluminium for structural uses.

The information in this publication is general in nature and is not intended for direct application

to specific technical or specific projects. European Aluminium cannot be held liable for any

damage, costs or expenses resulting from the use of the information in this publication. For

additional information please contact your aluminium supplier to discuss details directly with the

relevant experts.



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Chapter 2 - History of Aluminium Structures

Almost three centuries have passed since 1722, when Friedrich Hoffman, professor at the University of Halle

(Germany), announced the base of alum to be an individual substance. At the end of the eighteenth century the French

chemist Guyton De Morveau suggested to call this substance alumina, which is derived from the Latin word aluminis,

used in Egypt in the sixteenth century B.C. for indicating a material of dubious composition.

Following its isolation as an element and owing to the interest for the lightness and the brightness of such new metal,

efforts were therefore made to produce it industrially. A first step in this direction was done during the 1850s by the

French chemist Henry Sainte-Claire Deville, professor at the Sorbonne University in Paris. But it was only later, when

Paul Louis Toussaint Héroult (1863-1914) in France and Charles Martin Hall (1863-1914) in the USA set-up at the same

time the electrolytic process that paved the way for the industrial production of aluminium. As a result of the so-called

Hall-Héroult process a 200 times cheaper price for Aluminium was achieved. That was fundamental to launch large-

scale production of such material. In 1900 the industrial production of aluminium reached 8000 tons.

The properties of this new material impressed not only technicians, but also literates. Charles Dickens (1812-1870)

wrote: “Within the course of the last two years a treasure has been divined, unearthed and brought to light. What do

you think of a metal as white as silver, as unalterable as gold, as easily melted as copper, as tough as iron, which is

malleable, ductile, and with the singular quality of being lighter that glass? Such a metal does exist and that in

considerable quantities on the surface of the globe. The advantages to be derived from a metal endowed with such

qualities are easy to be understood. Its future place as a raw material in all sorts of industrial applications is undoubted,

and we may expect soon to see it, in some shape or other, in the hands of the civilised world at large”.

Charles Dickens’ prediction was correct: today aluminium is the second largest metal used worldwide and its

production is higher than the one of all non-ferrous metals together. The idea of Jules Verne may be associated to the

further applications in the modern aeronautic and aerospace industry.

The beginning of twentieth century assisted to the construction of

extraordinary structures: the airships (Fig. 2.1 and 2.2). They

consisted of a huge internal structure framework made of aluminium

in the shape of a cigar,

surrounded by a series of

cells filled with helium gas.

The most famous was the

Zeppelin, however the first

example was the Schwarz,

built in 1897. The dirigible aluminium structure is composed by transversal

rings connected by longitudinal beams; both have a reticulated structure: a

modern design concept now applied for example large span roofing

constructions. Figures 2.1 and 2.2 - The most famous dirigibles



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Some other striking examples are the statue of Eros

in London's Piccadilly, 1893 (Figure 2.3), the

aluminium sheets installed to clad the dome of the

San Gioacchino church in Rome, 1911 (Figure 2.4),

and the aluminium components installed in New

York's Empire State Building, 1931, the first building

to use anodised aluminium.

More recently in 1958, an extraordinary structure

was built for the Universal Exhibition of Brussels

and clad with aluminium: the Atomium, a 102

meter tall structure, which is half way between

sculpture and architecture, symbolising a ferrite

crystal made of 9 iron atoms, magnified 165 billion

times. Figure 2.3 - The Eros statue in Piccadilly circus, London

The aluminium cladding - initially conceived to last six months – has

served its purpose for almost 50 years. After the Atomium was

undergoing renovation (2004-2007): the original aluminium skin was

used for new purposes. A thousand aluminium triangular panels are

available for sale with a certificate of authenticity for collectors and

Atomium fans. The remaining 30 tonnes of aluminium have been

made available for recycling.

Today aluminium is the material of choice in many fields, ranging

from packaging, furniture, window, cladding of the buildings, to

automotive, airplane and offshore industry as well as to bridges and

civil engineering structures. In many of these fields, aluminium is out

of competition: one cannot fly, enjoy high speed trains, high

performance cars or fast ferries without it.

Figure 2.4 - San Gioacchino’s church, in Rome



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Figure 2.5 - The world’s largest aluminium boat, 130m long and 32m wide

Figures 2.6 and 2.7 - Production of aluminium train wagons



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Chapter 3 - Industrial production Process

Engineers responsible for the design of an aluminium structure are faced with two peculiarities. The first is the large

number of aluminium alloys combined with the different available tempers. The second is the fact that either as sheet

or as a standard section, only a limited range of alloys are available from stock. The reason for this is, while steel

structural sections are usually manufactured through rolling processes, aluminium sections for structural purposes are

often produced by means of hot extrusion. Rolling is characterised by high roll die costs in combination with

considerable changeover times and therefore needs large production quantities to keep costs as low as possible. When

looking at aluminium extrusions, die costs are low for small sections and increase only moderately for larger shapes.

The quantities to produce aluminium sections in a cost-effective way are relatively small and lie between 200 kg and

3000 kg depending on the size of the section. Consequently, many engineers and companies design specific sections

for their own projects in order to ensure high functionality. Ninety percent of all sections produced by aluminium

extruders are individually designed and are therefore only available for the use by the designer/purchaser of the

specific section.

This may explain why designing aluminium structures requires a deep knowledge of the material, especially when

compared to the design of steel structures. This chapter will investigate the properties of the most important alloys,

the system of designations of alloys and tempers and will dig into the availability of semi-finished products and their

relative costs.

3.1 Hardening of aluminium Pure aluminium itself is a metal with relatively low strength. Aluminium in its purest form has a tensile strength of

around 40 N/mm² and a yield strength of about 10 N/mm². Aluminium alloys however have been developed with

mechanical properties beyond those of the base material.

A very efficient means of producing material with greater resistance is to introduce suitable foreign elements into the

aluminium matrix (alloying). By introducing

suitable foreign metals into the aluminium

matrix it is possible to produce lattice

imperfections that allow better mechanical

performance of the material. One of the

elements which best suits the requirement to

improve strength is magnesium (see Figure

3.1). Aluminium-magnesium alloys were indeed

the predominant choice for structural

aluminium applications 100 years ago and

many years later.

Figure 3.1: Hardening effect as a function of the content of alloying element, here Mg



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3.2 Strain hardening Plastic deformation produces imperfections in the lattice by markedly increasing the number of so-called dislocations

particularly along the slip-planes. With increasing load and deformation, additional slip planes continuously develop

so that, with the resulting increase in dislocation density, the material increases its mechanical strength. Parallel to

this increase in strength, ductility decreases until ultimately the deformation process has to be stopped. When cold

rolling, this so called "work hardening” or "strain hardening" continues until the material begins to develop cracks.

However, the hardening process can be reversed using

heat. Depending on temperature and time, the gain in

material strength can be reversed and brought back to its

starting level before cold working. The material also

recovers its original ductility. This thermal process is

known as “annealing”. From this soft state the cold

working processes can be restarted. Fig. 3.2 shows the

effect of cold working and annealing on strength, here as

a function of time at constant temperature.

Figure 3.2: Work hardening and annealing

3.3 Precipitation hardening One or more suitable elements can form intermetallic compounds, i.e. particles bonded together with the aluminium

matrix. As seen before, such elements also constitute lattice imperfections and, depending on the size of these

particles as well as on their distribution, are responsible for considerable increase in strength. The whole precipitation

hardening process begins with the alloy being heated above a reference temperature and saturated there until a

homogeneous (solid) solution is produced. Then, quenching is necessary to get a uniform distribution of all elements

also at ambient temperature. After that, ageing ensures that the elements involved begin to diffuse in the aluminium

matrix, while numerous nucleation sites and precipitates grow and form intermetallic compounds.

3.4 Artificial ageing Natural ageing begins immediately after quenching at a relatively high speed but degressively and then asymptotically

approaches an upper limit (T4 in Figure 3.3). Depending on the alloy, the ageing process might take weeks, but for

most alloys this can be considered to be already concluded after one week. Artificial ageing can start hours (but also

days, depending on manufacturing needs) later. The material to be artificially aged is placed in a furnace, which allows

the ageing to be carried out under different temperature conditions. Typical for all temperatures is a quick hardening

that progressively reaches a maximum (T6). If the material is exposed to high temperatures for a longer time, the effect

of the precipitations on strength decreases and we get an over-aged temper (T7). In general, over-aged tempers are

characterised by better ductility, corrosion resistance (some copper and/or zinc containing alloys) and better electrical

conductivity.



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It must be emphasised that today

precipitation hardening alloys are

dominating in many areas (e.g. extruded

sections). They present a significant lower

deformation resistance during the (warm)

working processes, while gaining their

often-remarkable strength on a later

stage through precipitation hardening.

Figure 3.3: Strength in function of time at ambient and elevated temperature

3.5 Influence of Heat

The strength of aluminium, similarly to other materials, decreases when temperature increases. Up to certain

temperatures this phenomenon is still reversible, i.e. after cooling down the material has the same properties as

before. With temperatures up to 80 degrees Celsius, the drop in strength is negligible for all alloys and tempers. Over

80 °C some design situations could require creep effects to be considered. Heat-treatable alloys begin to lose strength

with temperatures over 110 °C depending on time. Non-heat-treatable alloys in work hardened tempers begin to lose

strength with temperatures over 150 °C - also depending on time. In 'O temper' non-heat-treatable alloys, no

permanent loss in strength occurs.

Welding causes much more severe losses in the strength of the

material. In case of welding, the temperatures are so high that the

effects of a decrease in strength in the vicinity of the weld (the so called

Heat Affected Zone HAZ) must be taken into account, as this often

constitutes an important aspect of the verification of the design of a

structure. The heat-treatable alloys in temper T6 (Fig 3.3) have a loss of

approximately 40% of their strength with the single exception of the

alloy EN AW-7020, which loses only 20% of its initial strength. To

facilitate design calculations, the area of strength losses is replaced by

a rectangular area with the width bhaz, which is standardised and may

depend on the material thickness in a range of some ten millimetres.

The strength value in this zone is also standardised and depends on

alloy and temper.

Figure 3.4: Reduction of strength in the heat affected zone

(HAZ) (typical for EN AW-6082)



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3.6 Alloys

In practice, only a few elements have proven to be suitable as alloying additions in aluminium wrought and cast

materials for structural applications. These are:

Copper (Cu); Manganese (Mn); Silicon (Si); Magnesium (Mg); Zinc (Zn)

They can be used as single elements as well as in combination. When working with aluminium alloys, it is necessary to know the nomenclature used with this material. This refers to the designation of the alloys in use and to the temper states in which they are supplied to the market.

3.6.1 Designation of wrought alloys

The numerical system developed by The Aluminium Association in the USA is today the most recognised system to

design wrought alloys worldwide. European Aluminium is among the signatories to the Declaration of Accord on an

International Alloy Designation System for Wrought Aluminium and Wrought Aluminium Alloys1.

Consequently, European standards also follow this nomenclature which makes use of a 4-digit number to further

designate the alloy. Wrought alloys are designated with the prefix "EN AW-". The first digit gives basic information

about the principal alloying element(s):

2xxx= Cu; 3xxx=Mn; 4xxx=Si; 5xxx=Mg; 6xxx=Mg+Silicon; 7xxx=Zn

The designation system also characterizes the hardening of the alloys belonging to a family. The 1xxx, 3xxx and 5xxx

series are so called non-heat-treatable alloys; they gain their strength by alloying (e.g. increasing content of Mg) and

work hardening. The 2xxx, 6xxx and 7xxx series are heat-treatable alloys, which gain their strength by alloying but

make use of precipitation hardening as the main mechanism.

In the past, several national standards used to designate alloys based on chemical symbols. For the engineer who was

not familiar with aluminium alloys, this was an advantage as it made possible to identify the characteristics of a given

alloy more easily (see Table 3.1 below).

Non heat-treatable alloys Heat treatable alloys

(Precipitation hardening alloys)

Numerical

Desig

nation

Chemical

Desig

nation

Form of Products Numerical

desig

nation

Chemical

Desig

nation

Form of products

EN AW- EN AW- sheet extru

sions

forging EN AW- EN AW- sheet extru

sions

forging

3004 AlMn1Mg1 X 6060 AlMgSi X

3005 AlMn1Mg0,5 X 6061 AlMg1SiCu X X

3103 AlMn1 X 6063 AlMg0,7Si X

1 https://www.aluminum.org/sites/default/files/Teal%20Sheet.pdf

https://www.aluminum.org/sites/default/files/Teal%20Sheet.pdf



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5005/500

5A

AlMg1(B)/(C) X 6005A AlSiMg(A) X

5049 AlMg2Mn0,8 X 6082 AlSi1MgMn X X X

5052 AlMg2,5 X 6106 AlMgSiMn X

5083 AlMg4,5Mn0,

7

X X X 7020 AlZn4,5Mg1 X X

5454 AlMg3Mn X X

5754 AlMg3 X X X

8011A AlFeSi X

Table 3.1. Wrought alloys listed in EN 1999-1-1

This is the reason why the European aluminium standards still use two principles for aluminium alloy designation:

numerical system specified in EN 573-1 and chemical symbols system specified in EN 573-2. Both systems are used in

EN 573-3 that provides the detailed chemical composition and form of products of wrought aluminium alloys.

3.6.2 Designation of casting alloys

The elements used for casting alloys are basically the same as for wrought alloys. However, for castings different

compositions are preferred. Casters prefer type 4xxxx alloys with high silicon content, since it ensures a good quality

production. Casting alloy designations have the prefix "EN AC-" to distinguish them from wrought alloys and have 5

digits in total. This system is European and not used in the USA.

Non heat treatable alloys

Heat treatable alloys

(Precipitation hardening alloys)

Numerical designation

Chemical designation

Numerical designation

Chemical designation

EN AC- EN AC- EN AW- EN AW-

51300 AlMg5 42100 AlSi7Mg0,3

44200 AlSi12(a) 42200 AlSi7Mg0,6

43000 AlSi10Mg(a)

43300 AlSi9Mg

Table 3.2. Casting alloys listed in EN 1999-1-1

The most frequently used alloys are EN AC-42100, -43000 and -44200. The alloys preferred by the foundries are EN

AC-43000, -43300 and -44200 due to their good castability. The alloy EN AC-51000 (AlMg5) is difficult to cast and



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therefore not popular at foundries and is therefore used quite occasionally despite the fact that engineers like to make

use of it due to its bright surface and anodisability (other alloys are more or less greyish, especially when anodised).

For more details, please refer to EN 1780-1, EN 1780-2 and EN 1780-3.

3.7. Tempers and designation of tempers 3.7.1 Tempers of non-heat-treatable alloys

Figure 3.2 explains the system in use for the definition of tempers for non-heat-treatable alloys. By increasing the

degree of cold working, ultimate strength and proof strength also increase. Nevertheless, there is a limit. For example

for temper H18 - fully hardened or 4/4 hard. The cold working process can be stopped earlier to get the tempers strain

hardened between O and H18, e.g. H14 or ½ hard. However, it is also possible to produce tempers with lower strength

than 4/4 hard, by annealing fully hardened material, i.e. H18. In this case, the material will be characterised by lower

strength values with a modified designation e.g. H24, i.e. "Strain hardened and partially annealed, 1/2 hard". In the

system is so that e.g. H14 and H24 have the same strength value, but the proof strength of H24 is a little lower (see

Figure 3.2), but its formability is better. Some more differentiations for the designation of tempers exist.

For the most relevant for non-heat-treatable alloys, see tables 3.1 and 3.2. For other temper please refer to the

standard EN 515.

Symbol Description

O Annealed (soft)

H 111 Annealed and slightly strain-hardened (less than H11)

during subsequent operations such as stretching or

levelling

H12 Strain-hardened, 1/4 hard

H22 Strain-hardened and partially annealed, 1/4 hard

H32 Strain-hardened and stabilized, 1/4 hard

H42 Strain-hardened and painted or lacquered -1/4 hard

H14 Strain-hardened, 1/2 hard

H18 Strain-hardened, 4/4 hard (fully hardened)

Table 3.3: Tempers in use for structural application of work hardened semi-products

(typical examples to explain the system)

3.7.2 Tempers of heat-treatable alloys

The complete heat-treatment consists of a solution heat-treatment, a quenching process and subsequent ageing,

where the actual hardening occurs. It must be said that, unlike steel, aluminium alloys are not hard immediately after

quenching.

To get the highest strength values it is important to keep the material at the correct solution heat temperature for

enough time and to follow the correct quenching procedure (see Figure 3.3 above). Depending on the alloy, this may



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be carried out using water or air. Heat-treatable alloys are produced in many tempers. For structural engineering only

a limited number is important and listed in Table 3.4.

Symbol Description

T4 Solution heat-treated and then naturally aged

T5 Cooled from an elevated temperature shaping process and

then artificially aged

T6 Solution heat-treated and then artificially aged

T61

T64

Solution heat-treated and then artificially aged in under ageing

conditions in order to improve formability (T64 between T61

and T6)

T66 Solution heat-treated and then artificially aged – mechanical

property level higher than T6 achieved through special control

of the process 6000 series alloys

T7 Solution heat-treated and artificially over-aged

Tx51

Tx510

Tx511

These suffixes stand for a controlled stretching to relieve

internal stresses coming from manufacturing

(the fourth digit characterises only variants – no influence on

characteristic values!)

Table 3.4: The main tempers in use for structural application of precipitation hardened semi-

products (T7 only listed to explain the system)

3.8 Alloys and tempers of alloys listed in the Eurocode 9

Considering their applicability for structural application and availability on the market, only a limited number of alloys

are included in the Eurocode 9. This is also true for the tempers of the alloys. Therefore, only the tempers which were

most frequently used in the past are listed, i.e. tempers H12, H14 and their corresponding partially annealed tempers

for work hardened materials. Higher strength tempers such as H16 and H18 are less common, since good forming

behaviour is often desired.

In EN 1999-1-1 (Part -1-1 of Eurocode 9), 17 wrought alloys are listed. They are used for products that have been

circulating for a long time on the European market and that have been approved by several national authorities.

EN 1999-1-1 offers a wide range of alloys and tempers to be used for structural applications. The range of strength, in

the sense of proof strength, varies from EN AW-5005 O with 35 N/mm² up to EN AW-7020 T6 with 290 N/mm².

For structural engineering the most commonly used alloys are:

• EN AW-6082, EN AW-6061 and EN AW-7020 (less frequently) for structures and components from sheet and extrusions of the same alloy

• EN AW-5083 and EN AW-5754 for structures and components from sheet (also in structures mixed with



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sections of other alloys) • EN AW-6060 and EN AW-6063 for structures and components from extrusions (also in structures mixed with

sheet of other alloys)

3.9 Practical viewpoints for the selection of materials

3.9.1 Sheet and plate

When designing aluminium structures, one must consider that sheets in small and mid-sized formats up to 1500x3000

mm are easy to obtain but the availability of more complex alloys and tempers is limited. EN AW-5083, -5754 and -

6082 are commonly available. Some specialised shipyard suppliers may also have larger dimensions on stock, but in

this case delivery time must be carefully taken into account. Sheets of non-commonly used aluminium alloys need

significant amount of orders with quantities of around 30-50 tons.

For structural engineering projects, it is often very important to know what the geometric limits are for the existing

production facilities of semi-products. Sheets and plates can be produced with widths of more than 3 m and lengths

of up to 22 m. The exact limits may depend on thickness and alloy. Most of the manufacturers deal with lengths under

10 m and widths up to approximately 2 m. When designing in sheets, it is also important to know that folding presses

with working widths up to 16m are not very common although facilities with more than 20 m do exist.

3.9.2 Extrusions

For aluminium extrusions, die costs are modest. Die changing needs only short times and therefore production batches

can be ordered for smaller quantities, normally between 200 and 3000 kg. This makes it possible for engineers to

design special sections, optimally adapting their requirements to the needs of each structural application. The

advantages are remarkable: reduced costs, low weight, transport facility, functional structural sections.

These specificities give tremendous advantages to extruded aluminium. In any case, it is recommended to check the

stock availability of semi-finished products whenever starting with the design of aluminium for structural applications.

In principle, extrusion works like squeezing paste out of a tube (Figure 3.5), a process the aluminium industry is

accustomed to performing on a daily basis all over the world by means of an extrusion press (Figure 3.6). Here, a

preheated aluminium billet (400 to 550 °C, depending on the alloy) is positioned in a preheated container. Under the

forces of the stem the material begins to flow through the die and so acquires the form defined by the die. While

aluminium is an extremely good material for extrusion, steel cannot be extruded.

Figure 3.5: Extruding toothpaste Figure 3.6: Extruding an aluminium bar



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3.9.3 Castings and forgings

Cast and forged parts are always individually designed parts and ordered directly from the manufacturer (if they are

not part of a system distributed via stockists). If no special experience exists, it is recommended that the engineer

contacts and collaborates closely with the manufacturer to determine the best design in combination with the alloy.

Depending upon alloy, foundry and size of the casting, the usual minimum quantity is in the order of 500-1000 pieces

but in special circumstances it may be possible to obtain somewhat smaller amounts. Sand cast parts are possible in

much lower quantities, depending on size and alloy. Production lots of 10 or 50 are not unusual. The procurement of

the casting alloys listed in EN 1999-1-1 is no problem for the

foundry, and small quantities can be supplied.

A similar situation applies to forged parts. In general, a batch of

1000 workpieces is required for an economically viable

manufacturing process Some manufacturers may produce smaller

quantities, in case the customer accepts the typically higher costs

associated. However, it may be a problem for the forging shop to

get the pre-material from the semi-product manufacturer in the

form or quantity needed. The alloys listed in EN 1999-1-1 are all

commonly used.

Figure 3.7 gives an idea of extruded aluminium sections used for

structural purposes. For the engineer not familiar with the design,

it is recommended to get in contact with a manufacturer and get

advice about suitable alloys to be chosen, possible tolerances of

the cross section, straightness etc. (e.g. based on EN 755, EN

12020)

For structural engineering, it may also be important to know what

the geometric limits are for the existing production facilities for

the semi-products. Figure 3.8 shows the limits for production in

Europe. Depending on cross section and alloy, profiles can be

produced with lengths up to 30 m. Normal stock length is 6 m.

Figure 3.7: Multiple possibility for sections

Figure 3.8: Upper dimensional limits for the design of extrusions



18

Chapter 4 - Why Aluminium in Structural Engineering

4.1 Basic prerequisites

The main difference between aluminium and steel is clearly emphasized by the comparison between the typical

products which characterize these materials (Figures 4.1 and 4.2). Steel hot rolled sections look strong, heavy and

rough; contrary aluminium extruded profiles which are various, light and elegant.

Figures 4.1 and 4.2: Typical steel and aluminium profiles

The success of aluminium alloys as constructional material and thus being a possible competitor to steel are based on

some prerequisites, connected to the physical properties, the production process and the technological features. It is

commonly recognised that aluminium alloys can be economical, and therefore competitive, in those applications

where full advantage is taken of the following properties:

A. Lightness: due to the low specific weight of aluminium alloys, which is one third of steel, it is possible to:

- simplify the assembly phases;

- transport fully prefabricated components;

- reduce the loads transmitted to foundations;

- economize energy either during assembly and/or in service;

- reduce the physical labour.

Significant examples of the advantages of this property are given in Figures 4.3 and 4.4, which show a floating dock

and a bridge span respectively moved by a crane and by a truck.



19

Figures 4.3 and 4.4: Examples of transportation of fully prefabricated structures.

B. Corrosion resistance: due to the formation of a protective oxide film on the surface, it is possible to:

- reduce the maintenance costs;

- provide good performance in corrosive environments.

C. Functionality of structural shapes, due to the extrusion process, makes it possible to:



20

- optimise the geometrical properties of the cross-section by designing a shape which simultaneously gives the

minimum weight and the highest structural efficiency;

- obtain stiffened shapes without using built-up sections, thus avoiding welding or bolting;

- simplify connecting systems among different component, thus improving joint details;

- combine different functions of the structural component, thus achieving a more economical and rational profile.

Examples of extruded aluminium profiles are shown in Figure 4.5. It can be observed that the double sections can be

adapted introducing bulbs and stiffeners to reduce local buckling effects. However, also by introducing a rail in the

middle of flanges for functional reasons. The T sections can also be improved by bulbs and stiffeners for strengthening

purpose, but the web can be doubled for improving the connecting system. Other sections, like L, Y and C are designed

with bulbs and stiffeners, which avoid local buckling.

Figure 4.5: Examples of extruded shapes

Figure 4.6 shows the nodal details of a crane bridge made of aluminium; each node is designed in such a way to improve

the connection with the bars. Node 1 is an upside-down T section which web is bifurcated to accommodate the

diagonal bars. The flange supports the two rails Node 2 is the tubular section of the upper chord with two expansions

for connecting the transversal bars. Node 3 is a stiffened C section with three expansions to connect both, the bottom

and the transversal bars, while the rail runs on the top flange.

Figure 4.6: Nodal details of a crane bridge



21

4.2 Fields of application

Some typical cases where aluminium can compete with shall be mentioned. They highlight the benefits of using

aluminium compared to steel, especially because of its main basic properties: lightness, corrosion resistance and

functionality. Used in civil engineering, aluminium can be successfully used for:

a) Long-span roof systems in which live loads are small compared with dead loads, as in the case of lattice space

structures and geodetic domes (Figures 4.7 and 4.8), covering large span areas, like halls, auditoriums.

b) Structures located in inaccessible places far from the fabrication shop, for which transport costs and ease of

erection are of extreme importance, such as electrical transmission towers, which can be carried by helicopter

already assembled (Figure 4.9).

c) Structures situated in corrosive or humid environments such as swimming pool roofs, river bridges, hydraulic

structures and offshore super-structures (Figure 4.10).

d) Structures having moving parts, such as sewage plant crane bridges and moving bridges, where lightness means

economy of power under service (Figure 4.11).

e) Structures for special purposes, for which maintenance operations are particularly difficult and must be limited, as

in case of masts, lighting towers, antennas, tower signs, motorway signs, etc.

In general, the same main pre-requisites are fruitfully exploited in all kinds of applications in “Structural Engineering”.

Table 4.1 illustrates a series of structural applications which are grouped according to the three basic properties. L for

lightness; C for corrosion resistance; F for functionality. The seven lists correspond to the main influence of one

property (L, C, F separate) or to the combination of two (C+F, C+L, F+L) or three (C+L+F).

All together, they represent the choices in which the use of aluminium is potentially advantageous and, therefore,

competitive with steel.

Figure 4.7: ENEL aluminium dome, Rome (Italy)



22

Figure 4.8: A typical geodetic dome (Epcot Centre, Florida)

Figure 4.9: A prefabricated bridge transported by helicopter Figure 4.10: The superstructures of an offshore platform



23

Figure 4.11: Aluminium bridge with maintenance-free movable deck, Amsterdam (the Netherlands)

Table 4.1: Structural applications grouped according to the prevalence of

the three basic properties lightness (L), corrosion resistance (C), functionality (F)



24

Chapter 5 - Design of aluminium structures according to Eurocode 9

5.1 Introduction

The current version (2007, as amended in 2009) of Eurocode 9: Design of aluminium structures is composed of five

documents:

- Part 1-1: General structural rules

- Part 1-2: Structural fire design

- Part 1-3: Structures susceptible to fatigue

- Part 1-4: Cold-formed structures

- Part 1-5: Shell structures

Part 1-1 General structural rules

Contrary to the other Eurocodes, EC9 consists of just one part, which is divided into one basic document “General

structural rules” and four specific documents, which are related to the basic one. There are no separate documents

dealing with specific types of structures, like in steel (i.e. bridges, towers, tanks …). Eurocode 9 looks instead at general

items which are applicable not only to the range of the so-called “Civil Engineering”, but more widely to any kind of

structural applications in the wider field of “Structural Engineering”, including also the transportation and offshore

industries. Some rules for bridges and lattice spatial roof structures are given in annexes to Part 1-1.

The main features of the calculation methods in Part 1-1 are given in the following sections.

Part 1-2: Structural fire design

As in all Eurocodes, Part 1-2 is devoted to fire design. For aluminium structures, fire design has been codified for the

first time according to general rules, which assess the fire resistance based on three criteria: Resistance (R), Insulation

(I) and Integrity (E).

Aluminium alloys are generally less resistant to high temperatures than steel and reinforced concrete. Nevertheless,

by introducing rational risk assessment methods, the analysis of a fire scenario may in some cases result in a more

beneficial time-temperature relationship and thus make aluminium more competitive and the thermal properties of

aluminium alloys (e.g. high thermal conductivity) may have a beneficial effect on the temperature development in the

structural component.

Part 1-3: Structures susceptible to fatigue

The knowledge on the fatigue behaviour of aluminium joints has been consolidated during the last 30 years. In 1992,

the European Recommendations on Fatigue Design of Aluminium Alloy Structures were published, representing a

fundamental basis for the development of EC9. In its Part 1-3: Structures susceptible to fatigue, it is possible to find

general rules applicable to all kind of structures under fatigue loading conditions with respect to the limit state of

fatigue induced fracture. Three design methods have been introduced:

– Safe life design;

– Damage tolerant design;

– Design assisted by testing.



25

Eight basic groups of detail categories have been considered, including:

– non-welded details;

– members with transverse and longitudinal welded joints and attachments;

– bolted joints;

– special aluminium mechanically joints such as bolt channel joints and screw groove joints;

– adhesively bonded joints.

The use of finite elements and the guidance on assessment by fracture mechanism have been suggested for stress

analysis. The importance of quality control on welding has been particularly emphasised in general, and specific

reference to EN 1090 “Execution of steel and aluminium structures” has been taken into consideration (see also

Chapter 7).

Part 1-4: Cold-formed structures

Part 1-4 is mainly referred to the use of trapezoidal sheeting. It is similar as the corresponding steel part EC3-1-3, but

the effective thickness method is used instead of the effective width one.

Part 1-5: Shell structures

Part 1-5 has been built-up by following the same format of the similar document EC3-1-6, but the calculation methods

are based on appropriate buckling curves which are obtained on the bases of the experimental evidence on aluminium

shells.

5.2. Main aspects to consider when designing aluminium structures

This is a summary of the main aspects to be considered when designing aluminium structures, as they are very different from steel.

Weight

Low weight (g = 2 700 kg/m3) is particularly important where the weight of the structure is a dominant factor and where the low weight permits a vehicle to carry a greater load. Low weight is also important during the transport and assembly of a structure. Examples of weight savings are given in Tables 5.1 and 5.2.

Deflection

As the modulus of elasticity of aluminium is low (E = 70 000 MPa), the deflection check is a priority issue. Deflection requirements are often critical in aluminium structures, for example when the deflection should not be greater than four-hundredths of the span of a beam. Often the strength is not fully exploited and simple approximations are adequate for the check of the resistance. A simplified method to allow for local buckling and softening in the Heat Affected Zone (HAZ) is given in EN 1999-1-1, 6.4.

If the deflection of a beam in bending is the critical factor, the stiffness EI must be the same as in steel. Because the modulus of elasticity E of aluminium is one third that of steel, the moment of inertia 𝐼al for the aluminium beam must be 3𝐼steel. If the height of the beam is not increased, the flange area must be increased by a factor of three and, because the density of aluminium is one third of that of steel, this means that the aluminium beam will have the same weight as the steel beam. If, on the other hand, it is acceptable to increase the height of the beam, a considerable weight saving can be made by choosing aluminium. This is illustrated in Table 5.2, where an IPE 240 steel beam is compared with some alternative aluminium beams.



26

tw

b

t f

h

Material steel aluminium aluminium aluminium

Moment of inertia 𝐼/mm4 38.9 ⋅ 106 116.6 ⋅ 106 116.7 ⋅ 106 117.3 ⋅ 106

𝐸𝐼/MNm2 8,17 8,17 8,17 8,17

ℎ/mm 240 240 300 330

𝑏/mm 120 240 200 200

𝑡𝑤/mm 6.2 12 6 6

𝑡𝑓/mm 9.8 18.3 12,9 10

Weight /kg/m 30,7 30,3 18,4 15,8

Weight in % of steel beam 100% 99% 60% 51%

Table 5.1: Beams with same stiffness

Strength-to-elastic modulus ratio

Most of the structural aluminium alloys have relatively high “strength-to-elastic modulus” ratio. This effect is especially clear when the aluminium alloy is strain-hardened or heat-treated. Structural aluminium alloys have roughly twice the strength-to-elastic modulus ratio than standard steels. However, when compared with high strength steels, structural aluminium alloys have about the same ratio.

This large strength-to-elastic modulus ratio means that, if an aluminium structure is designed according to deflection criteria, the stress is very often low. It also means that if the design of the structure is based on strength it is often possible to save weight by using aluminium. This is illustrated in Table 7, where it can be seen that the weight is not very much depending of the height of the section in these examples.



27

tw

b

t f

h

Material steel aluminium aluminium aluminium

𝑓𝑦 or 𝑓o /MPa 355 260 260 260

Moment resistance /kNm 108 108 108 108

ℎ/mm 240 240 300 330

𝑏/mm 120 120 120 120

𝑡𝑤/mm 6.2 8.0 7.0 6.0

𝑡𝑓/mm 9.8 14.2 11.5 11.0

Weight /kg/m 30.7 13.8 12.9 12.3

Weight in % of steel beam 100% 45% 42% 40%

Table 5.2 – Beams with same moment resistance

Strength reduction after welding

Aluminium alloys used in structural applications are strengthened by heat-treating or cold working. This means that the strength of the alloy is reduced locally by welding, hot-straightening or hot-forming.

6xxx alloys in T6 temper lose roughly half of their strength in the heat affected zone when welded. Alloys in T4 temper generally retain their strength. See Chapter 3.6

The strength of alloys can be restored by artificial ageing after welding.

To avoid reduction of the load-bearing resistance, welds should - if possible - be situated in areas where stresses are low, such as the neutral axis of a beam in bending.

Fatigue

When fatigue may be a key design factor, it must be considered that the fatigue strength of a welded part is roughly 40% of that of steel. No problems arise for not welded structural members.

Relatively low hardness

It is suggestable to avoid unnecessary transport and components that, because of their size and shape, are prone to deformation or surface damage. For hardness values, see Chapter 3.6.

Not prone to brittle fracture at low temperatures

Contrary to steel, aluminium does not become brittle at low temperatures, as it does not have a brittle transition temperature. Aluminium tends to become tougher, stiffer and stronger at low temperatures.

Low damping factor

Where oscillation is induced by varying imposed frequencies, such as gusts of wind, the structure should be made stiff enough to ensure that the natural frequency is considerably higher than the largest imposed frequency.



28

High thermal expansion

The coefficient of thermal expansion is twice that of steel. i.e. 0.000023/°C. Changes in ambient temperature and other temperature variations must be considered, if the corresponding movement could result in significant forces. However, because of the low modulus of elasticity, the stresses caused by restrained expansion are moderate. For instance, if a beam is rigidly fixed at the ends, a temperature change produces a stress state in an aluminium beam, which is 2/3 of that in a steel beam.

High thermal conductivity

The high thermal conductivity means for instance that the temperature differences on both sides of a profile equalize quickly.

High corrosion resistance

Corrosion resistance is often a key reason for choosing aluminium. See Chapter 4. Aluminium normally does not require corrosion protection. Attention should however be given to the risks of standing water and crevice corrosion.

Extrudability

Extrusion technology offers many possibilities for creating tailor-made profiles. It is often profitable to produce a special profile even for moderate quantities. See Chapter 3.9.2.

Formability and machining

Aluminium is easily worked even in the cold state, especially in low states of temper. Aluminium can be formed in press brakes and roll presses and can be deep-drawn, deep-pressed, hydroformed, etc.

Tight cross-sectional tolerances

Extruded profiles with open cross-sections are produced to tight tolerances and can be produced in very straight lengths by stretching after extrusion. Cross-sectional tolerances for hollow profiles can be slightly larger.

Low residual stress

In contrast to hot-rolled steel profiles, extruded aluminium profiles have low residual stresses in the longitudinal direction. This advantage respect to steel can be found also in built-up aluminium sections, despite of heat-affected zones, due to the low elastic modulus and the high thermal conductivity.

5.3. Limit state design

Limit state design and partial safety factor are the methods which the design standards are based upon. In Europe the EN 19xx standards (Eurocodes) are the basis for the structural design of all structural materials in civil engineering. For the design of aluminium structures, the complete standard package to be followed is the following:

– EN 1990 Eurocode 0 – Basis for structural design, which gives the partial safety factor on loads and rules for combination of loads to give the different action effects.

– EN 1991 Eurocode 1 – Actions on structures, which gives the characteristic loads for structures and buildings such as self-weight, live loads (Part 1-1), wind loads (Part 1-4), snow loads (Part 1-5), action during execution (Part 1-6), traffic loads on bridges (Part 2) etc.

– N 1999 Eurocode 9 – Design of aluminium structures, which gives the design rules for aluminium structures.

National Annex

National standards implementing the European standards have a National Annex containing Nationally Determined



29

Parameters to be used for the design of building and civil engineering structures in the relevant country. These National Annexes can give other values of relevant parameters (e.g. of partial factors), than the ones which are recommended in the Eurocodes. Notes in the Eurocodes indicate where national choices are allowed.

Limit states

According to the Eurocodes, calculations should be carried out for the two limit states:

– Serviceability limit state;

– Ultimate limit state.

The serviceability limit state sets the requirements for normal use. For aluminium structures it imposes requirements on deflection and, in some cases, vibration. As mentioned above, this limit state is often the critical design situation for aluminium structures because of the aluminium's low modulus of elasticity. Normal loads (i.e. without partial safety factors and also low combination factors) are used in this check.

The ultimate limit state is used to check that the structure has adequate strength regarding material failure, instability (torsional, lateral torsional and flexural-torsional buckling) and collapse. Fatigue and strength when exposed to fire are further ultimate limit states.

5.4. Serviceability limit state

As already mentioned, it is important to check deflection and other deformations in aluminium structures. It is often required to check that the calculated deflection for a beam is less than a value which depends on the span. EC 9 does not give any limits for deflection. According to EN 1990 – Basis of structural design, limits for deflections should be specified for each project and agreed with the owner of the construction work. The National Annex to the code can specify limits for deflections and limits for vibration of floors.

Examples of limits for deflections are given in Table 5.3. A deflection > 𝐿/200 can usually be seen with the naked eye.

Design situation Deflection limit, 𝐿 = span

Floor beams in buildings 𝐿 /400 + vibration requirements

Road bridge 𝐿 /600

Railway bridge 𝐿 /800

Spectator stands 𝐿 /400

Beams carrying plaster or other brittle finish 𝐿 /400

Purlins and sheeting rails on roofs Typically, 𝐿 /200 and 25 mm to avoid ponding (damming up water to form a small pool)

Glass facades and roofs 𝐿 /200

Table 5.3: Examples of vertical deflection limits

Calculation of deflections and deformations in the serviceability limit state are elastic calculations and normally based on the moment of inertia for the gross cross-section of the member. However, for members in cross-section class 4 (cf. Chapter 5.6.2) the moment of inertia should be reduced according to 7.2.4 in EN 1999-1-1.



30

5.5. Ultimate limit state method

The ultimate limit state is the situation where the safety of the structure is checked. A structure shall not collapse and design in accordance with the ultimate limit state shall avoid structural failure. The partial safety factor for the resistance (𝛾M) shall take care of the scattering of the strength properties and the geometry of the cross-section.

The partial safety factor for the load effects (𝛾Q and 𝛾G) shall take care of the scattering in the determination of the

loads and of the probability in the combination of different loads. The partial safety factor is different for the different types of loads, their uncertainty and how they are combined. Dead loads (i.e. self-weight of the structure) have a low partial safety factor, while the live loads (i.e. all forces that are variable during operation, e.g. snow loads, wind load, imposed loads in buildings, traffic loads …) have a higher partial safety factor.

EkR k<

MQ

E k Rk

Load effect E

Resistance RFrequency

γ γ Gk

R k

MG

Dead load effect G

Resistance RFrequency

γ γ

Gk

Rk

Figure 5.1 – Illustration of the partial factor method

The condition to be fulfilled is (see Figure 5.1):

kQ k

M

RE

where:

𝐸k is the characteristic value of the load effects; it may be axial tension or compression, bending moment, shear or a combined load effect on a cross-section or on a connection.

𝑅k is the characteristic value of the resistance; it may be axial tension or compression, bending moment, shear or a combined resistance.

𝛾M is the partial safety factor for the resistance, also called material factor.

𝛾Q is the partial safety factor for the load effects, also called load factor.

Typical values for the partial safety factor for the resistance are 1.10 (𝛾M1) for members and 1.25 (𝛾M2 and 𝛾Mw) for bolt and rivet connections and welded connections.

These are the material factors for building and civil engineering structures and may also be used in all structural design because the material, the geometrical dimensions and the fabrication of connections are almost similar in all aluminium structures.

Typical values for the load effect factors in buildings and civil engineering are 1.2 – 1.3 for dead loads and 1.5 for live loads. These factors may also be used for the design of components for other structures, like commercial vehicles.



31

5.6. Ultimate limit state for members

5.6.1 General

Buckling class for materials, cross-section class, effective thickness to allow for local buckling and HAZ as well as methods for members in compression and bending are specific to Eurocode 9. These are therefore presented in more details in the following paragraphs. Further rules and methods are listed, and references are given in Tables 5.4 and 5.5.

The resistance of a member in compression depends on material properties, cross-section type and dimensions and member properties. Material properties like strength and Buckling Class (BC) (see 5.6.2), together with cross-section properties constitutes the cross-section class which depends on the slenderness b/t of the cross-section parts, see Figure 5.2.

The cross-section class defines the stress distribution at the ultimate limit state and thus how the cross-section resistance is calculated.

Material Buckling Class and HAZ define which buckling curve should be used and, together with member length, support conditions and cross-section resistance, the resistance of the member can be calculated.

5.6.2 Cross-section class

Cross-sections are classified in 4 classes. In Figure 5.2, the stress distribution for the different classes are shown which identify how the cross-section behaves during bending. This is directly linked to the resistance of the cross-section. Limits for b/t for the different classes are given Table 6.2 of EC 9. For Buckling Class, slenderness b/t and cross-section class, see also items 3, 4 and 5 in the overview in 5.6.6 A).

Class 1, "ductile": The resistance may be calculated based on plastic behaviour taking the hardening of the material into account. Plastic hinges can develop in a continuous beam or frame.

Class 2, "compact": The resistance may be calculated based on plastic behaviour without hardening. Elastic theory is used for continuous beams or frames.

Class 3, "semi-compact": The cross-section can develop elastic or partly plastic resistance. Elastic theory is used for continuous beams or frames.

Class 4, "slender": Thin parts of a cross-section may buckle before attainment of the proof stress. The resistance is based on an effective cross-section. Elastic theory is used for continuous beams or frames. Usually the reduction of the stiffness due to local buckling in the calculation of the moment distribution is omitted.

Material

properties

0,2% proof strength

Ultimate strength

BC (σ - ε -diagram)

HAZ

Cross-

section

Member

supports

Internal/outstand parts

Symmetric/asymmetric

Open / closed

Slenderness b/t

Length (span)

Simple/fixed support

Part of frame

Cross section class

fo Wpl ≥ foWel fo WeffMRk = afoWel

Cross section resistance

Resistance

Buckling curve

1 2 43

Figure 5.2: Scheme to calculate member resistance



32

5.6.3 Material Buckling Class (BC) and buckling curves

The buckling resistance of aluminium columns depends merely on initial bow (geometrical imperfection), residual

stresses (structural imperfection) and stress-strain relationship. Furthermore, size and position of HAZ due to heat

introduction during welding affect buckling resistance of longitudinally welded columns.

For steel members the residual stresses are the most important factor and, as the magnitude and distribution of the

residual stresses depends on the cross-section type, there are different buckling curves for different cross-section

types in the Eurocode for steel. As already mentioned, the residual stresses for extruded aluminium profiles are very

small. However, the stress-strain relationship is strongly non-linear from the origin, which is the reason why, in the

case of aluminium, the choice of buckling curves for extruded profiles depends on the alloy and temper expressed by

the Buckling Classes A and B. In Figure 5.3 examples of stress-strain curves for the two Buckling Classes are shown.

The corresponding buckling curves are designated 1 and 2 (see Figure 5.4).

For longitudinal welded aluminium members, however, there are residual stresses where the distribution is similar

as in welded steel members. Although, compared to yield strength, the magnitude in aluminium is smaller than in

steel. Nevertheless, the influence on the buckling resistance is similar as for steel, so the resistance should depend

on the cross-section type. However, as aluminium members can have many different cross-section shapes and, for

sake of simplicity, a reduction factor is given in Table 6.6 in EC9 for class A and class B materials.

0,01 0,020

100

300

200

σ

ε A

B1

B2

0

Figure 5.3: Example of a stress-strain curves for Buckling Class A and two curves for Buckling Class B

Figure 5.4: Reduction factor χ for flexural buckling

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2,00,5 1,0 1,5

12



33

5.6.4 Effective thickness due to local buckling and HAZ softening

Contrary to steel, the effective thickness method instead effective width method is used to take reduction of

resistance due to local buckling into account. Besides simpler calculations, the advantage is that combination with

local reduction of the 0,2% proof strength 𝑓o,haz and of the ultimate strength 𝑓u,haz in HAZ is simpler (see Figure 5.5).

ro,haztf

bc

bh

az

teff = rctf

t f

min(ro,haztw; rc,wtw)

bhazb

tw

rc,wtw

z

ro,haz < rc

bc

bh

az

teff = rctft f

min(ro,haztw; rc,wtw)

bhazb

tw

rc,wtw

z

ro,haz > rc

ro,haztf

a. The reduction in HAZ is less than the reduction

due to local buckling

b. The reduction in HAZ is larger than the reduction

due to local buckling

Figure 5.5 – Effective cross-section of class 4 compression part of welded member

The severity of softening in HAZ is generally larger in BC A than in BC B material, where for some material the

reduction is null or very small. For example, the 0,2% proof strength in HAZ is half the strength in the base material

for EN-AW 6082-T6, whereas for temper T4 of the same alloy the reduction is just 10% according to Table 5.2 a) of

Eurocode 9.

5.6.5 Bending and axial compression

The procedure and formulae for bending and axial compression are different from them for steel. In Eurocode 9, there are two special means to cover the influence of local buckling, plastic strain and second order effects:

– exponents 𝜂𝑖, 𝛽𝑖 and 𝛿𝑖 on the terms in the interaction formulae to account for plastic strain and local buckling, where 𝑖 = 𝑦 or 𝑧 depending in buckling direction (formula below);

– factor ,x y and , ,LTx y to take the second order moment distribution along the member into account.

NEd

l cr

x

y MEd(x) NEd × y

+ =

MEd,2(x)+ =NEd

QEd

ωx = χ

ωx = 1

Figure 5.6: Moments and 𝝎𝒙-diagram for a member in bending and compression



34

As an example, the formula for lateral-torsional buckling is:

+ +

c zc

z,Rd

y,Ed z,EdEd

, ,LT y,LT, z Rd y,Rd

1,00

c

x yx z

M MN MN M

With these exponents and factors, the same interaction formulae can be used for all cross-section classes 1 to 4.

The three terms in the formula are measures of how much the respective resistances are used due to axial force, y-y-axis bending (including influence of lateral-torsional buckling) and z-z-axis bending. They are therefore called utilization grades. The first term includes the influence of the bending moment of the axial force times the deflection.

The exponents, which are depending on the shape factors 𝛼𝑦 and 𝛼𝑧, result in different shape of the interaction

curves for different cross-sections (see Figure 5.7). For compression and strong axis bending, the shape factor is up to 1,15 with rather small plastic reserve in the web after that plastic strain started in the flanges. For weak axis bending the reserve is larger with shape factor up to 1,5 and slightly larger. This results in curves which are strongly convex upwards. For cross-section class 3 the curves start with straight lines for shape factor = 1 to strongly convex curves for class 2 cross-sections. As the exponents are functions of the shape factor, there is a smooth transition between class 2 cross-sections to class 4 cross-sections represented by the curves for cross-section class 3.

1,5

N

Npl

Mz

Mpl,z

00

0,5

0,5

1,0

1,0

zz

1,4z = 1,0 1,1 1,2 1,3

class 4

Class 2

Class 3

1,15

N

Npl

My

Mpl,y

00

0,5

0,5

1,0

1,0

Class 4

Class 2

1,12

y = 1,0

1,031,061,09

yy

Class 3

Figure 5.7: Interaction diagrams for strong axis and weak axis bending

and compression of H-beams in different cross-section classes

The factor taking the distribution of the second order moment along the member into account is included in the interaction formula which, for strong axis buckling, is

y,EdEd

y,RdRdy

1,00

yc

x

N M +

N M

where the factor is

𝜔𝑥 = 1/ (𝜒 + (1 − 𝜒) 𝑠𝑖𝑛𝜋𝑥

𝑙cr)



35

𝜉𝑦𝑐 = 𝛼𝑦2 ⋅ 𝜒𝑦 ≤ 0.8;

𝛼𝑦 is the shape factor;

𝜒𝑦 is the reduction factor for flexural buckling.

The 𝜔𝑥 factor is smallest in the middle of the span, where (𝑙cr being the buckling length)

𝑥 = 𝑙cr/2 so 𝜔𝑥 = 1/ (𝜒 + (1 − 𝜒) 𝑠𝑖𝑛𝜋

2) = 1 and

Ed Ed

Rd Rdy yx

N N

N N =

which is the utilization grade for buckling.

At the support

𝑥 = 0 so 𝜔𝑥 = 1/𝜒𝑦 and

Ed Ed

Rd Rdyx

N N

N N =

which is the utilization grade for section resistance as it is no second order bending moment in a simple support.

In between the utilization grade of the axial force follow 1/𝜔𝑥 which is the inverse of a sine curve. This is illustrated in Figure 5.8 a), where the grey part corresponds to the influence of the moment of the axial force times the deflection.

M1,Ed

My,Rd

M2,Ed

My,Rd

NEd

NRd

NEd

NRd

max

X = 1

x

X = 1/

NEd

NRd

(a) (b)

+

NEd

NRd

MEd

My,Rd+x

M 2 = M 1

M 1

(a) (b)

NEd

NRd

CmM1MRd

kyy +

+

(c)

NEd

NRd

M1MRd

+(d)

Figure 5.8 – Compression and bending according to the Eurocodes 9 for aluminium

Figure 5.9: Compression and bending according to the Eurocodes 3 for steel

This utilization grade due to the axial force is added to the utilization grade of the bending moment with arbitrary distribution, as shown in Figure 5.8 (b). (The exponents on the utilization grades have been omitted for clarity). The sum of the utilization grades should be less than 1 in every section along the member. In the example in Figure 5.8 maximum of (a)+(b) occur where a line parallel to the moment diagram is a tangent to the sine curve.



36

In the Eurocode for steel, the principle is to find a constant moment which gives correct result together with constant utilization grade 𝑁Ed/(𝜒𝑦𝑁Rd), which means that a lot of factors are needed. This is illustrated in Figure 5.9

where the actual moment diagram (a) is transferred to an equivalent constant moment (b) which is then combined with the utilization grade due to the axial force (c). It is then necessary to check the resistance at the ends (d) separately.

As the exponent 𝜉𝑦𝑐 in this case is depending on the reduction factor 𝜒𝑦, the interaction curves will be convex

downwards for large relative slenderness. See example in Figure 5.10 (a).

With this estimation of the utilization grade along the member, it is possible to check reduction of localized HAZ due to transverse weld in any section along the member.

Ec 9

0 0,5 1,0

1,0

Class 2

0

1,0

y = 0

y = 0,62

y= 1,23

y =

N EdNRd

0,5

y,Ed

y,Rd

M

M

Ec 9

0

0,5

1,0

0

Class 3

y=

y = 0

y = 1,23

y = 0,62

y,Ed

y,Rd

M

M

0 0,5 1,0

NEd

NRd

(a) (b)

Figure 5.10 – Interaction curves for flexural buckling for (a) uniform moment and (b) variable moment

5.6.6 Overview of the main design provisions in EN 1999

Relevant rules and design formulae according to Eurocode 9 are summarized in the following, divided in groups of

topics. The numbers of reference of Sections, Figures and Tables correspond to the 2007 version of Eurocode 9, as

amended in 2009.

A) Material strengths, partial factors, Buckling Classes, cross-section classes, local buckling and HAZ

Subject Reference to

EN 1999-1-1

Notations and limits

1. Material strengths 3.2

𝑓𝑜 is the characteristic 0,2% proof strength for bending and

overall yielding in tension and compression



37

Table 3.2 (a to e)

Table 3.3

6.2.1

𝑓𝑢 is characteristic ultimate tensile strength for the local

capacity of a net section in tension or compression

𝑓𝑤 is characteristic strength of the weld metal

Values for sheets, strips and plates are given in Table 3.2a and

values for extruded profiles in Table 3.2b. For forgings values are

given in Table 3.2c and for gravity castings in Table 3.3.

If formulae in 6.2.2 to 6.2.10 do not apply, formula (6.15) can be

used.

2. Partial factors 6.1.3 𝛾M1 is used for the resistance of cross-sections and resistance of

members to instability based on 𝑓o. Recommended value is

1,1.

𝛾M2 is used for the resistance of cross-sections to fracture and

resistance of joints in tension, shear and bearing based on 𝑓𝑢

or 𝑓𝑤. Recommended value is 1,25.

3. Material Buckling Class

BC

0,01 0,020

100

300

200

σ

ε A

B1

B2

0

3.2.2, 6.1.4.4,

6.1.5, 6.3.1

Table 5.2 a) and

b)

The resistance if instability is involved (local, flexural, lateral

torsional … buckling) is depending on the shape of the stress-

strain curve. As this curve is different for different materials, the

materials and tempers are divided into two Buckling Classes A

and B.

The Buckling Class for the alloys are given in Table 5.2 a) and b).

Effective thickness and buckling curve are depending on the

Buckling Class, but also if a member is longitudinally welded or

not.

4. Slenderness

6.1.4.3

𝛽 = 𝜂𝑏

𝑡

𝑏 is the width of a cross-section part

𝑡 is the thickness of a cross-section part

𝜂 is the stress gradient factor

𝜂 = 0,70 + 0,30𝜓 (1 ≥ 𝜓 ≥ −1)

𝜂 = 0,80/(1 − 𝜓) (𝜓 < −1)

𝜓 is the ratio of the stresses at the edges of the plate under

consideration related to the maximum compressive stress.



38

Slenderness limits 6.1.4.4, Table 6.2 Limits for the cross-section classes denoted 𝛽1, 𝛽2 and 𝛽3 are

given in Table 6.2.

5. Cross-section class

Limits for cross-section

parts of members in

bending

6.1.4.2

6.1.4.4

Class 1 cross-sections are those that can develop their plastic

moment resistance forming a plastic hinge with the rotation

capacity required for plastic analysis.

The hardening effect may be taken into account according to

Annex L.

𝛽 ≤ 𝛽1

Class 2 cross-sections are those that can develop their plastic

moment resistance but have limited rotation capacity

because of local buckling.

The resistance is based on perfectly plastic behaviour.

𝛽1 < 𝛽 ≤ 𝛽3

Class 3 cross-sections are those in which the calculated stress in

the extreme compression fibre can reach its proof strength,

but local buckling is liable to prevent development of the full

plastic moment resistance.

The resistance is based on elastic or partly plastic behaviour.

𝛽2 < 𝛽 ≤ 𝛽3

Class 4 cross-sections are those in which local buckling will occur

before the attainment of proof strength in compression in

any part of the cross-section.

The resistance is based on an effective cross-section.

𝛽 > 𝛽3

6. Local buckling 6.1.5

6.1.5, Table 6.3

Local buckling in class 4 members should be taken into account by

replacing the true section by an effective section, obtained by

employing a local buckling factor 𝜌𝑐 to reduce the thickness.

Factor 𝜌𝑐 is depending on the material Buckling Class and should

be computed from formulae (6.11) or (6.12), separately for

different parts of the section. The factor is different for internal

cross-section parts and outstand parts and depends on whether

the member is longitudinally welded or not.

7. HAZ 6.1.6

The characteristic value of the 0,2 % proof strength 𝑓o,haz and of

the ultimate strength 𝑓u,haz in the heat affected zone should be

taken from Table 5.2, which also gives the reduction factors



39

6.1.6.3

𝜌o,haz =𝑓o,haz

𝑓𝑜 and 𝜌u,haz =

𝑓u,haz

𝑓𝑢

Local buckling effects and effects due to HAZ softening should be

included by means of the effective thickness.

The extent of 𝑏haz of HAZ depends on the plate thickness and the

welding method.

8. HAZ and local buckling 6.2.5.2, for

example see

Figure 5.5 above

For class 4 part with HAZ effects, the effective thickness is taken

as the lesser of that corresponding to the reduced thickness 𝑡eff

and that corresponding to the reduced thickness 𝜌o,haz𝑡 in the

softened part, and as 𝑡eff in the rest of the compressed portion of

the cross-section.

9. Transverse welds 6.3.1.1, 6.3.3.3 At a section with transverse weld 𝜌o,haz is replaced by 𝜌u,haz. The

reduction due to local welds is depending on where the reduction

is located along the member, less reduction at the end than at the

span of a member in compression. This is accomplished with the

𝜔x expression.

10. Holes 6.2.2.2, 6.3.3.4 The resistance is based on the net area through the section with

the holes.

B) Resistances for different design situations

Design

situation

Reference to

EN 1999-1-1

Resistance

1. Tension

6.2.3 The smallest of:

general yielding along the member 𝑁o,Rd = 𝐴𝑔𝑓𝑜/𝛾M1

local failure at a section with holes 𝑁net,Rd = 0,9𝐴net𝑓𝑢/𝛾M2

local failure at a section with transverse weld 𝑁u,Rd = 𝐴u,eff𝑓𝑢/𝛾M2

𝐴g is either the gross section or a reduced cross-section to take into

account HAZ softening due to longitudinal welds. In the latter

case 𝐴g is found by taking a reduced area equal to 𝜌o,haz times

the area of the HAZ;

𝐴net is the net section area, with deduction for holes and a deduction,

if required, to take into account the effect of HAZ softening in the

net section through the hole. The latter deduction is based on

the reduced thickness 𝜌u,haz𝑡;

𝐴u,eff is the effective cross-section area based on the reduced thickness



40

𝜌u,haz𝑡;

2.

Compression

with no

buckling

6.2.4 The smallest of:

in sections with unfilled holes 𝑁net,Rd = 𝐴net𝑓𝑢/𝛾M2

in sections with transverse weld 𝑁u,Rd = 𝐴u,eff𝑓𝑢/𝛾M2

in other sections 𝑁o,Rd = 𝐴eff𝑓𝑜/𝛾M1

𝐴net is the net section area, with deductions for unfilled holes and HAZ

softening, if necessary. For holes located in reduced thickness

regions the deduction may be based on the reduced thickness,

instead of the full thickness;

𝐴eff is the effective section area based on reduced thickness taking into

account local buckling and HAZ softening due of longitudinal welds

but ignoring unfilled holes;

𝐴u,eff is effective section area, obtained using a reduced thickness 𝜌𝑐𝑡

for class 4 parts and reduced thickness 𝜌u,haz for the HAZ

material, whichever is smaller.

3. Bending

moment

t f,e

f

tw,ef

6.2.5

6.2.5.2

6.2.5.1

The smallest of:

in a net section 𝑀net,Rd = 𝑊net𝑓𝑢/𝛾M2

in section with transverse weld 𝑀u,Rd = 𝑊u,eff𝑓𝑢/𝛾M2

in any cross-section 𝑀o,Rd = 𝛼𝑊el𝑓𝑜/𝛾M1

𝑊el is the elastic modulus of the gross section;

𝑊net is the elastic modulus of the net section taking into account

holes and HAZ softening, if welded. The latter deduction is

based on the reduced thickness of 𝜌u,haz𝑡;

𝑊u.eff is the effective section modulus, obtained using a reduced

thickness c tr for class 4 parts and reduced thickness 𝜌u,haz𝑡

for the HAZ material, whichever is smaller;

𝛼 is the shape factor given in Table 6.4. If elastic design is used

for class 1, 2 and 3 cross-sections, then 𝛼 = 1 (for members

with longitudinal welds 𝛼 = 𝑊el,haz/𝑊el).

(Some notations are here not the same as in the code for clarity, e.g

𝑀o,Rd here and 𝑀c,Rd in the code)

4. Shear and

transverse

load

6.2.6

The design shear resistance for non-slender sections



41

6.7.4,

6.7.5

6.7.6

𝑉Rd = 𝐴𝑣

𝑓𝑜

√3𝛾𝑀1

𝐴v is the shear area

For slender webs and stiffened webs, the resistance for plate girders

webs should be used.

The design resistance for transverse loads are given in 6.7.5 and

interaction in 6.7.6.

5. Torsion

SC GC

6.2.7 The design St. Venant torsion moment resistance without warping (e.g.

closed sections)

𝑇t,Rd = 𝑊𝜏,pl

𝑓𝑜

√3𝛾𝑀1

𝑊𝜏,pl is the plastic torsion modulus.

For torsion with warping the torsion moment is the sum of two internal

effects 𝑇Ed = 𝑇t,Ed + 𝑇w,Ed.

Where the torsional moment is combined with a shear force, the

resistance is given by a reduced shear strength.

Torsion can be avoided by shaping the cross-section so that the shear

centre SC is located in the plane of the loading. Closed cross-sections

can resist large torsion moments.

6. Bending

and shear

6.2.8 If the shear force is less than half the shear resistance its effect on the

moment resistance can be neglected, otherwise the shear force will

reduce the moment resistance.

7. Bending

and axial

force

6.2.9

6.3.3

Interaction formula are given in 6.2.9. They are the ground for the

formulae for buckling resistance of members in bending and

compression in 6.3.3.

8. Bending,

shear and

axial force

6.2.10 If the shear force is less than half the shear resistance, its effect on the

combined axial force and moment resistance can be neglected,

otherwise the shear force will reduce the bending and axial force

resistances.

9. Web

bearing

6.2.11

6.7.5

The design of un-stiffened or longitudinally stiffened webs subjected to

localised forces caused by concentrated loads or reactions applied to a

beam is based on formulae for plate girders.



42

10. Buckling

resistance of

member in

compression

See also

6.6.5 above.

6.3.1

Table 6.5

6.3.1.2

Figure 6.11

Members subject to axial compression should be considered to fail in

one of three ways:

• flexural

• torsional or flexural torsional

• local squashing

The design buckling resistance of a compression member without

transverse welds is

𝑁b,Rd = κ𝜒𝐴eff/𝛾M1

𝜒 is the reduction factor for the relevant buckling mode, material

Buckling Class;

𝐴eff is the effective area taking into account local buckling and HAZ

softening of longitudinal welds. For torsional and torsional-

flexural buckling see Table 6.7. (For class 1, 2 and 3 cross-sections

without longitudinal welds, 𝐴eff = 𝐴g);

𝜅 is the a factor to allow the weakening effect of longitudinal

welding given in Table 6.5. If there are no welds, then 𝜅 = 1.

The reduction factor 𝜒 is a function of the relative slenderness

�̄� = √𝐴eff𝑓𝑜

𝑁cr=

𝐿cr

𝑖

1

𝜋√

𝐴eff

𝐴

𝑓𝑜

𝐸

Two curves are given, designated 1 and 2.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 2.00.5 1.0 1.5

1

2

For a member with localised welds, the resistance is reduced at the

section with the weld. The resistance is depending on where the weld is

located along the member defined by the function 𝜔x.



43

6.3.3.5

11. Lateral

torsional

buckling of

member in

bending

6.3.2

Table 6.4

6.3.3.5

Lateral torsional buckling may be neglected in any of the following

cases:

a) bending takes place about the minor principal axis;

b) the member is fully restrained against lateral movement throughout

its length;

c) the relative slenderness �̅�LT between points of effective lateral

restraint is less than 0,4.

The design buckling resistance moment of a laterally un-restrained

member should be taken as

𝑀b,Rd = 𝜒LT𝛼𝑖𝑊el,y𝑓𝑜/𝛾M1

𝑊el,y is the elastic section modulus of the gross section, without

reduction for HAZ softening, local buckling or holes;

𝛼𝑖 is the shape factor subject to the limitation 𝛼𝑖 ≤ 𝑊pl,𝑦/𝑊el,𝑦;

𝜒LT is the reduction factor for lateral torsional buckling.

12. Members

in bending

and axial

compression

6.3.3

6.3.3.1

6.3.3.2

Members subject to bending and axial compression may fail in one of

the two modes

• flexural buckling

• lateral-torsional buckling

Interaction formulas are given for members with axial compression in

combination with bending about one or two axis and fail for flexural

buckling. These formulas are given for:

• open double symmetric cross-section

• solid cross-section

• hollow cross-section and tube

• open mono-symmetrical cross-section

Interaction formula for lateral- torsional buckling of open cross-section

symmetrical about major axis, centrally symmetric or double symmetric

cross-section is given.

Formulas are also given for the following effects:



44

6.3.3.3

6.3.3.4

6.3.3.5

• members containing localized welds

• members containing localized reduction of cross-section

• unequal end moments and/or transverse loads

13. Plate

girders

6.7

6.7.2,

6.7.3

6.7.4, 6.8

6.7.6

6.7.5

6.7.7

6.1.5

6.3.2

A plate girder is a deep beam with a tension flange, a compression

flange, and a web plate. The web is usually slender and may be

reinforced by transverse or/and longitudinal stiffeners.

Webs buckle in shear at relatively low applied loads, but considerably

amount of post-buckled strength can be mobilized due to tension field

action.

Plate girders are sometimes designed with transverse web

reinforcement in form of corrugations or closely spaced transverse

stiffeners (extrusions).

Plate girders can be subjected to combinations of moment, shear, and

axial loading, and to local loading on the flanges. Because of their

slender proportions they may be subjected to lateral torsional buckling,

unless properly supported along the length.

Failure (buckling) modes may be:

• web buckling by compressive stresses

• shear buckling

• interaction between shear force and bending moment

• buckling of web due to local loads on flanges

• flange-induced web buckling

• torsional buckling of flange (local buckling)

• lateral torsional buckling

14. Stiffened

panels

6.6

6.7

Un-stiffened plates as separate components under in-plane loading is

given in 6.6 and 6.7.

The same applies for stiffened plates under in-plane loading. Out-of-

plane loading is not treated in EC9.



45

15. Cold-

formed

structures

EN1999-1-4 Provisions for cold-formed structural sheeting are given in EN 1999-1-4.

16. Shells EN1999-1-5 Provisions for shell structures are given in EN 1999-1-5.

C) Design of joints

1. Basis of

design

8.1.2

Annex M

The forces and moments applied to joints at the ultimate limit state

should be determined by global analysis including:

— second order effects;

— the effects of imperfections;

— the effects of connection flexibility.

D) Connections made with bolts, rivets and pins

2. Spacings 8.5

Table 8.2

The rules for bolted connections are given in 8.5, where minimum,

regular, and maximum spacing, end and edge distances for bolts are

given.

3. Slotted,

oversized

holes, etc

8.5.1,

8.5.7

Table 8.4,

8.5.14

Long and short slotted holes and oversized holes are treated.

Countersunk bolts and rivets.

Pin connections.

4. Categories

for shear

connections

8.5.3.1 Category A: Bearing type;

Category B: Slip-resistant at serviceability limit state;

Category C: Slip-resistant at ultimate limit state.

5. Categories

for tension

connections

8.5.3.2 Category D: Connections with non-preloaded bolts;

Category E: Connections with preloaded high strength bolts.

6. Failure

modes

Table 8.5 Failure modes for bolted connections may be:

• block tearing, failure in shear in a row of bolts along the shear face of

a bolt group and tension failure along the tension face of the bolt

group;

• shear failure in the bolt;

• bearing failure of the bolt hole;

• tension failure of the bolt;



46

• punching shear around the bolt head or nut;

• combined shear and tension failure.

7. Prying

forces,

equivalent T-

stub in

tension

8.5.10

Annex B

Connection details that carry tensile forces, and where the tensile

forces do not go directly through the bolts, additional forces in the bolts

have to be accounted for. These forces are called prying forces (Q) and

they can be considerable large. See the Figure 5.11. Prying action is

important for T-stub in tension. See Annex B.

2FEd

Q Q

FEd + Q FEd + Q

leff

Figure 5.11: Prying action for T-stub in tension

E) Welded connections

1. General 3.3.4

3.3.4

EN 1011-4

The rules given in EC9, clause 8.6, apply to structures welded by MIG or

TIG and with weld quality in accordance with EN 1090-3. Certified

welders are highly recommended. Recommended welding consumables

can be found in the references to the left.

2. Strength

values

Table 5.2

Table 8.8

When welding hardened aluminium alloys, part of the hardening effect

will be destroyed. In a welded connection it can be three different

strengths:

• the strength in the parents (not heat affected) material (𝑓o, 𝑓u);

• the strength in the heat affected zone (𝑓o,haz, 𝑓u,haz);

• the strength of the weld metal (𝑓𝑤).



47

3. Check in

weld and

HAZ

Table 5.2

Table 8.8

Normally it will be necessary to check the stresses in the HAZ and in the

welds. The strength in HAZ is dependent on the alloy, the temper, the

type of product and the welding procedure.

The strength in the weld (weld metal) is dependent on the filler metal

(welding consumables) and the alloys being welded.

4. Single

sided butt

welds

8.6.3.2.2 Single sided butt welds with no backing is practically impossible to weld

in aluminium. If single sided butt welds cannot be avoided, the effective

seam thickness can be taken as:

• the depth of the joint preparation for J and U types;

• the depth of the joint preparation minus 3 mm or 25%, whichever is

the less for V or bevel type.

In addition to the single sided butt weld, a fillet weld may be used to

compensate for the low penetration of the butt weld.

5. Practical

precautions

8.6.1 When designing a welded connection some few practical precautions

should be taken into account.

• Provide good access to the welding groove. The “welding head” of the

equipment used for welding aluminium is rather large, so there must be

enough space around the weld.

• Good access is also needed for checking the weld. All welds shall be

100 % visually examined in addition to some non-destructive testing

(NDT).

• Full penetration single sided butt welds are impossible to weld

without any backing.

• If possible, position the welds in areas where the stresses are low.

6. Butt welds 8.6.3 Heavy loaded members should be welded with full penetration butt

welds. The effective thickness of a full penetration butt weld should be

taken as the thickness of the thinnest connecting member. The

effective length should be taken as the total length if run-on and run-off

plates are used. If not, the total length should be reduced by twice the

effective thickness. (Figure 5.12).

7. Design

formulae for

butt welds

8.6.3.2 Normal stress, tension or compression, perpendicular to weld axis:

𝜎⊥ ≤ 𝑓𝑤/𝛾Mw

Shear stress: 𝜏 ≤ 0.6𝑓𝑤/𝛾Mw

Combined normal and shear stress: √𝜎⊥2 + 3𝜏2 ≤ 𝑓𝑤/𝛾Mw



48

8. Fillet

welds

8.6.3.3 A fillet weld is defined with the throat thickness “a” given in mm. The

Figure 5.12 shows how to measure the throat thickness. The effective

length should be taken as the total length of the weld if:

• the length of the weld is at least 8 times the throat thickness;

• the length of the weld does not exceed 100 times the throat thickness

with a non-uniform stress distribution;

• the stress distribution along the length of the weld is constant.

9. The forces

acting on a

fillet weld

The forces shall be resolved into stress components with respect to the

throat section (see Figure 43)

These components are:

𝜎⊥ normal stress perpendicular to the throat section;

𝜎|| normal stress parallel to the weld axis;

𝜏⊥ shear stress acting on the throat section perpendicular to the weld;

𝜏|| shear stress acting on the throat section parallel to the weld axis.

a

z

t 2

t1

a pen

a

||

(a)

||

a

F

Figure 5.12

10. Heat

affected

zone

Figure 8.21 The stress in the heat affected zone has to be checked. The stress is

calculated for the smallest failure plane for both butt welds and fillet

welds. The sketches in Figure 5.13 indicate the failure plane for some

welds:

W: weld metal, check of weld;

F: heat affected zone, check of fusion boundary;

T: heat affected zone, check of cross-section.



49

T Tt

T

t

F

F

t t e

T T

W W W

Figure 5.13

F) Friction Stir Welding, FSW

1. Friction

Stir Welding

8.9 With the friction stir welding process, the weld is produced by a

rotating tool which plastically softens the material at both sides of the

weld line which preferably should be long and plane. Depending on the

material thickness, the process requires stiff and strong welding fixtures

and supports. Full penetration butt welds and lap joints can be

produced, but not conventional fillet welds. Because the temperatures

are below the melting point, welding problems which may occur with

MIG or TIG welding are avoided.

2. Alternative

structures

Figure 5.14 a) Single sided weld welded from one side, Figure 5.15 (1);

b) profiles welded from top (2) and bottom (3);

c) profile welded with half overlap from top (2) and bottom (3).

t t

2

3

t

2

3

t t

1

a)

c)b)

t

Figure 5.14: Friction Stir Welds, FSW

No design provisions are given for Friction Stir Welding in the 2007 version of EC9, as amended in 2009.

However, these will be available in the new version of EC expected to be published in 2023.

G) Bolt-channel joints and screw grooves



50

1. Bolt

channel

8.9 The bolt-channel joining system consists of an extruded profile with a

groove that is shaped to host the head or the nut of the bolts

connecting the profile to the other components, see Figure 5.15 (a).

When the connection is composed by more bolts arranged at a certain

distance, a plate with threaded bolt holes can be inserted in the guide,

see Figure 5.15 (b).

L b

p 1

p 1

p 2

p 2

(a) (b)

Figure 5.15: Bolt channels

(a) (b)

Figure 5.16: Screw grooves

No design provisions are given for bolt channels and screw grooves the 2007 version of EC9, as

amended in 2009. However, these will be available in the new version of EC expected to be published in

2023.

H) Adhesive bonded joints

1. Structural

adhesive

bonded joint

Annex M Adhesive bonding needs an expert technique and should be used with

great care. The design guidance in Annex P should only be used under

the condition that:



51

— the joint design is such that only shear forces have to be

transmitted;

— appropriate adhesives are applied;

— the surface preparation procedure before bonding do meet the

specifications as required by the application.

The use of adhesive for main structural joints should not be

contemplated unless considerable testing has established its validity,

including environmental testing and fatigue testing if relevant.

2. Use Annex M.4 Adhesive joining is very much used in specific structures (aeroplanes,

vehicles) and can be suitably applied for certain building and civil

engineering structures such as plate/stiffener combinations and other

secondary stressed conditions.

3. Loaded

area

Annex M.4 Loads should be carried over as large an area as possible. Increasing the

width of joints usually increases the strength pro rata. Increasing the

length is beneficial only for short overlaps. Longer overlaps result in

more severe stress concentrations, in particular at the ends of the laps.

4. Strength Annex M.5 The strength of an adhesive joint depends on the following factors:

a) the specific strength of the adhesive itself;

b) the alloy, and especially its proof strength if the yield stress of the

metal is exceeded before the adhesive fails;

c) the surface pre-treatment: chemical conversion and anodising, use

of primers;

d) the environment and the ageing;

e) the configuration of the joint and the related stress distribution;

Laboratory tests taking into account the whole assembly, i.e. the

combinations of alloy/pre-treatment/adhesive, and the ageing or

environment are important.

I) Fatigue

1. General Structures with repeating loads may be susceptible to fatigue when the

number of load cycles is high, even when the loads give low stresses in

the structure. Fatigue failure starts with development of a crack at a

point with stress concentrations. With continuous repeating loads the

crack will grow, this will be shown as one striation in the failure surface



52

for each load cycles. The distance between the striations is depending

on the stress range and that is giving the growing speed.

2. Standards EN 1999-1-3

EN 1090-3

Rules for fatigue design are given in EN 1999-1-3. The rules are based

on quality levels given in EN 1999-1-3 and EN 1090-3.

3. Fatigue

strength

EN 1999-1-3,

6.1, 6.2

The fatigue strength depends on:

• type of detail (design);

• stress range;

• number of cycles;

• stress ratio;

• quality of manufacturing.

4. Stress

range

EN 1999-1-3,

5.1.1

The stress range is defined as the algebraic difference between the

stress peak and the stress valley in a stress cycle (Figure 5.17). At low

stress ranges the crack grows slowly and with high stress range it grows

fast.

max

T 20

min

m

a

a

1

3

Figure 5.17: Stress range -1. Stress peak, 2. Stress valley, 3. Stress cycle, Δσ Stress range, σ_a Stress amplitude

5. Fatigue

strength

EN 1999-1-3,

6.2

The properties of the parent material have very little influence on the

fatigue strength in practical structures and components. For

connections, the properties of the parent material have no influence at

all. For a plate or extrusion with no manufacturing or only holes and

notches the standard deviate between EN AW 7020 and all other

structural alloys.

The fatigue strength is given as SN curves for the different details. All

detail categories given in EN 1999-1-3 have their own SN curve. A

typical SN curve is shown in the Figure 5.18.



53

2.106

NC

5.106

ND NL

a

m1

1

c

d

C

D

L

m2

1

N

b

10 1010101010 5 98764

Figure 5.18: a. Fatigue strength curve; b. Reference fatigue strength; c. Constant amplitude fatigue limit; d. Cut-off limit

6. Detail

Category

EN 1999-1-3,

Annex J

EN ISO

10042

EN 1090-3

Some typical details categories are shown in the Table J.1 The first

column in the table gives the detail type number, the second row gives

the detail category, the third gives a sketch of the detail and also

showing the initiation site and the direction of the stress, the fourth

gives the weld type, the fifth gives the stress parameter, the sixth gives

the welding characteristics, the seventh gives the quality level for the

internal imperfections and the eight gives the quality level for the

surface and geometrical imperfections. The requirements for the

quality levels are found in EN ISO 10042 and additional requirements

are given in EN 1090-3.

Detail Types 5.1 and 5.2 are examples where the same detail has

different fatigue strength depending on the weld method. Detail type

13.1 and 13.2 show that an attachment (especially a long attachment)

can have a detrimental influence on the fatigue strength.

The SN curves that correspond to these detail categories are shown in

Figure 5.19.



54

63-4,356-4,3

104 109108107106105N

50

40

100

150

200

300

400

500

30

20

15

10

5

NC NLND

N/mm2

23-3,4

18-3,4

Figure 5.19 - Example of fatigue strength curves

L) Examples of detail categories

Part of Table J.5 in EN 1999-1-3

5.1 63-4,3 At weld discontinuity

Full

pen

etra

tio

n

bu

tt w

eld

. We

ld

cap

s gr

ou

nd

flu

sh

No

min

al s

tres

s at

in

itia

tio

n s

ite

Continuous automatic welding

B C

5.2 56-4,3 C C

Part of Table J.13 in EN 1999-1-3

13.1 23-3,4

> tt

Weld toe

Transverse attachment, thickness < 20 mm, welded on one or both sides

Net

sec

tio

n

Stif

fen

ing

eff

ect

of

atta

chm

ent

/ st

ress

co

nce

ntr

atio

n a

t “

har

d

po

int”

of

con

nec

tio

n

C C

For

web

-to

-fla

nge

fill

et w

eld

s, s

ee

Tab

le J

.5, t

ype

no

. 5.4

or

5.5

13.2 18-3,4

Weld toe

Longitudinal attachment

length 100 mm, welded on all sides



55

Chapter 6 – Examples of applications by using Eurocode 9 The low value of the elastic modulus E has a big influence on the deformations of aluminium structures, which means

that the deformation at the serviceability limit state is often governing the design. The designer should not forget to

check the deformation before the final check of the strength at the ultimate limit state.

References to clause, Table or formula in Italic refer to EN 1999-1-1 (2007 version, as amended in 2009). For reference

to another Eurocode, EN number is also given in Italic.

Example 1: Vertical deflection and resistance of a simply supported beam

Design data

A simply supported glass roof beam of span 4.2 m (Figure 6.1) is subjected to the following un-factored loads:

Dead load 8.6 kN/m

Imposed roof load 10.5 kN/m

Snow load 6.8 kN/m

Serviceability limit state

Design an I-beam for the vertical deflection limit = span/360 (beam carrying plaster or other brittle finish).

From clause 5.2.5 we find 270000 MPa (N/mm )E = .

The characteristic combination of action according to EN 1990 is used with all partial factors = 1.

𝐸𝑑 = ′𝐺𝑘 ′ + ′𝑄k,1′ + ′𝜓0,2𝑄k,2′

where the permanent action kG is unfavourable and the imposed roof load ,1kQ is the leading variable action.

From EN 1991, for snow loads at altitude > 1000 m, 0 0.7 = . Therefore

𝑞 = 8.6 + 10.5 + 0.7 ⋅ 6.8 = 23.9 kN/m

tw

b

t

h

L

q

Figure 6.1: Simply supported beam and beam cross-section

Under a uniform distributed load, the maximum deflection w of a simply supported beam is given by

𝑤 =5

384

𝑞𝐿4

𝐸𝐼



56

from which the required second moment of area is solved

𝐼req =5

384

𝑞𝐿4

𝐸𝑤

For a deflection limit of span/360 for brittle finish we get

𝐼req =5

384

𝑞𝐿4

𝐸𝑤=

5

384

23.9 ⋅ 42004

70000 ⋅ (4200/360)= 1.18 ⋅ 108 mm4

As there are no standard I-beams in aluminium, the flange slenderness is chosen to avoid reduction due to local

buckling. For EN-AW 6063-T6, 𝑓𝑜 = 160 MPa, class A, without weld, the slenderness limit is

𝛽3 = 6휀 = 7.5 for 휀 = √250/160 = 1.25.

Choose flange slenderness 𝑏

𝑡= 2𝛽3 =15.0.

An approximate formula for the second moment of area is

𝐼 ≈ 0.58𝐴𝑓ℎ2 , where 𝐴𝑓 = 𝑏𝑡 from which, for a chosen value h = 308 mm of the beam depth,

𝐴𝑓 =𝐼req

0.58ℎ2=

1.18 ⋅ 108

0.58 ⋅ 3082= 2150 mm2

As 𝑏 = 2𝛽3𝑡 = 15.0𝑡 , it results

𝑡 = √𝐴𝑓

2𝛽3= √

5150

15= 12.0 mm and 𝑏 = 2𝛽3𝑡 = 15 ⋅ 12.0 = 180 mm.

Chose web thickness w 6 mmt = and check the resulting second moment of area:

𝐼 = 2𝑏𝑡 (ℎ

2)

2+

𝑡𝑤ℎ3

12= 2 ⋅ 180 ⋅ 12 ⋅ 1542 +

6⋅3083

12= 1.17 ⋅ 108 mm4 ≈ 𝐼req , accepted.

As h is the distance between the centres of the flanges, then the total height will be 308 + 12 = 320 mm.

Ultimate limit state

Check the resistance with the simplified analysis method according to clause 8.4.

The design load combination according to EN 1990 is used

𝐸𝑑 = ′𝛾𝐺𝐺𝑘 ′ + ′𝛾𝑄𝑄𝑘,1′ + ′𝛾𝑄𝜓0,2𝑄k,2′ , where the partial factors are 𝛾𝐺=1,2 and 𝛾𝑄=1,5.

It results

𝑞𝐸𝑑 = 1.2 ∙ 8.6 + 1.5 ∙ 10.5 + 1.5 ∙ 0.7 ⋅ 6.8 = 33.2 kN/m

𝑀Ed = 22.2 ⋅ 4. 22/8 = 49.0 kNm

As 𝑏

2𝑡=

180

2⋅12= 7.5 = 𝛽3 cross-section class is 3 and 𝜌𝑚𝑖𝑛 =1.0

𝑀𝑅𝑑 =𝜌𝑚𝑖𝑛𝑊el𝑓𝑜

𝛾M1=

1.0∙1.17⋅108

308

2

160

1.1= 1.11 ∙ 108 Nmm = 111 kNm > 𝑀Ed = 49.0 kNm , passed.



57

Example 2: Bending moment resistance of a class 4 cross-section

Aluminium profiles may have very different and complicated shapes. Examples of a series of profiles used in curtain

walls and windows are shown in Figure 6.2.

1 2 3 4 5 6

Figure 6.2: Examples of typical aluminium profiles for curtain walls and windows

Design data

The cross-section may have bolt channels and screw grooves, which may work as stiffeners of the slender parts of the

cross-section. Number 3 profile of Figure 6.2 is chosen as an example of a class 4 cross-section for bending.

b

h

tw

sc

t ft b

y

z

zg

c

zu

kz

ue tw.eftw.ef

z

a) actual cross-section (b) effective cross-section (simplified)

Figure 6.3: Extruded aluminium profiles: (a) actual cross-section; (b) effective cross-section



58

The aim is to calculate the major axis bending moment resistance for the upper flange in compression. The material is

EN-AW 6063-T6 which, according to Table 3.2, belong to Buckling Class A and has a proof strength o 160 MPaf = . The

partial factor of strength is M1 1.1 = .

The cross-section is complicated. However, most CAD programs give the “ordinary” cross-section constants: 𝐴 =

1073 mm2, 𝐼𝑦 = 3.00 ⋅ 106 mm4, 𝑊𝑦,el = 3.93 ⋅ 104 mm3 and 𝑧gc = 72.1 mm.

To check local buckling, also the following geometrical data are necessary:

𝑏 = 50 mm, 𝑡𝑓 = 3.5 mm, ℎ = 140 mm, 𝑡𝑤 = 2 mm, 𝑧ue = 77.5 mm, and for the bottom flange 𝑡𝑏 = 7 mm and

ℎ𝑛 = 17 mm, see Figure 6.3.

The influence of the web stiffeners (screw ports) close to the centre of the webs is small and omitted when calculating

the major axis moment resistance. Contrary, for axial force they may have noticeable influence.

Cross-section classification

In Table 6.2, 휀 = √250/160 = 1.25.

For the flange, clause 6.1.4.3(1): 𝛽𝑓 = (𝑏 − 2𝑡𝑤)/𝑡𝑓 = (50 − 2 ⋅ 2)/3.5 = 13.1.

Slenderness limit, Table 6.2 : 𝛽2 = 16휀 = 16 ⋅ 1.25 = 20 and 𝛽1 = 11휀 = 11 ⋅ 1.25 = 13.8;

flange is Class 1.

For the web, clause 6.1.4.3(1), the stiffeners are neglected. As the tension flange is very much stiffened, the web is

supposed to start at the middle of the bottom screw port. Then

𝜓 = −𝑠𝑐 − 𝑧ue

𝑧ue − 𝑡𝑓= −

125 − 77.5

77.5 − 3.5= −0.642

𝛽𝑤 = (0.7 + 0.3𝜓)(𝑠𝑐 − 𝑡𝑓)/𝑡𝑤 = (0.7 + 0.3 ⋅ (−0.642))(125 − 3.5)/2 = 30.8

𝛽2 = 16휀 = 16 ⋅ 1.25 = 20 and 𝛽3 = 22휀 = 22 ⋅ 1.25 = 27.5 ;

web is Class 4.

Shape factor

The section classification is Class 4 and the shape factor is then based on the effective cross-section according to Table

6.4 in clause 6.2.5.1. As the compression flange is Class 1, only the web thickness needs to be reduced.

For the material Buckling Class A according to Table 3.2b, the coefficients in formula (6.12) are 𝐶1 = 32 and 𝐶2 = 220,

so

𝜌𝑐 = 𝑚𝑖𝑛 [𝐶1 𝛽𝑤− 𝐶2 (

𝛽𝑤)

2, 1.0] = 32

1.25

30.8− 220 (

1.25

30.8)

2= 0.936. (6.12)

The effective thickness of the compression part of the webs is

𝑡w,ef = 𝜌𝑐𝑡𝑤 = 0.936 ⋅ 2 = 1.872,



59

where the width of this part is

𝑏𝑐 = ℎ − 𝑡𝑓 − 𝑧gc = 140 − 3.5 − 78.1 = 58.4 mm.

Again, the CAD program is used. The section modulus for the upper edge (ue) and bottom edge (be) of the section are

found to be almost identical

𝑊ue = 3.828 ⋅ 104 mm3 and 𝑊be = 3.827 ⋅ 104 mm3.

Sometimes an iteration procedure is needed to assure that the width of the compression part of the web coincides

with the calculated neutral axis for the effective cross-section, see clause 6.2.5.2(2) and clause 6.7.2(5). However, this

is not necessary in this case as the overall cross-section is almost symmetric. The shape factor is then

𝛼4 =𝑚𝑖𝑛( 𝑊ue, 𝑊be)

𝑊el=

3.827

3.933= 0.973.

Bending moment resistance

Bending moment resistance is according to (6.25)

𝑀o,Rd = 𝛼4𝑊el𝑓𝑜/𝛾M1 = 𝑊eff𝑓𝑜/𝛾M1 = 3.827 ⋅ 104 ⋅ 160/1.1 = 5.57 kNm (6.25)

Example 3: Bending moment resistance of a welded member with a transverse weld

Design data

Two extruded channel sections are welded together to a rectangular hollow section according to Figure 6.4. Calculate

the major axis bending moment resistance for

a) section without transverse weld;

b) section with transverse butt welds across part of the web.

The material is EN-AW 6082-T6, which, according to Table 3.2b, belong to Buckling Class A and has a proof strength

of = 260 MPa. The partial factor of strength is M1 1.1 = .

Width b = 100 mm, height h = 300 mm, flange thickness f 10t = mm and web thickness w 6t = mm.

Resistance of section without transverse weld

Cross-section classification, clause 6.1.4

Classification based on limits in Table 6.4 for BC A, with welds gives cross-section class 3 for the flange. For the web for

BC A, without welds, cross-section class is also 3.



60

t f

bw hht

b

bi

tw

2bhaz

2bhaz

HAZ

l wb

ha

zb

ha

z

l w +

2b

ha

z

2bhaz

2bhaz

Figure 6.4: Welded aluminium profile

Heat affected zones, clause 6.1.6

The reduction factor for the strength in HAZ is found in Table 3.2b, and the extent is found in clause 6.1.6.3

𝜌o,haz = 0,48 and 𝑏haz = 30 mm for f 10t = mm.

The effective thickness within HAZ will be

𝑡haz = 𝜌o,haz 𝑡𝑓 = 0.48 ⋅ 10 = 4.8 mm.

The elastic section modulus allowing for HAZ is found by deleting the difference between the flange thickness and the

effective thickness within the width haz2b from the gross cross-section.

For the gross cross-section 𝐼𝑦 = 8.926 ⋅ 107 mm4

For the reduced cross-section 𝐼y,haz = 𝐼𝑦 − 2𝑏haz(𝑡𝑓 − 𝑡haz)2 (ℎ𝑡

2)

2= 7.61 ⋅ 107 mm4

The section modulus 𝑊el,haz = 𝐼y,haz2/ℎ = 5.08 ⋅ 105 mm3

The plastic section modulus allowing for HAZ

𝑊pl,haz =1

4(𝑏ℎ2 − (𝑏 − 2𝑡𝑤)(ℎ − 2𝑡𝑓)2) − 2𝑏haz(𝑡𝑓 − 𝑡haz)ℎ𝑡 = 6.09 ⋅ 105 mm3

Shape factor, clause 6.2.5.1

For cross-section class 3 the shape factor = 1.0 or may alternatively be calculated using (6.27). As the web area is a

large part of the cross-section, formula (6.27) in clause 6.2.5.1 is used.



61

pl,haz el,hazel,haz 33,w

elel 3 2

WW - W = +

W - W

−

(6.27)

where the cross-section part with the smallest value of the ratio 3 3 2( ) / ( ) − − is the critical part. The web is

decisive so

3,w 0.937 = . (6.27)

Bending moment resistance

Bending moment resistance is according to (6.25)

𝑀o,Rd = 𝛼3,w𝑊el𝑓𝑜/𝛾M1 = 132 kNm (6.25)

Resistance of section with transverse weld, clause 6.2.5.1

The resistance in section with the transverse weld is given by formula (6.24).

𝑀u,Rd = 𝑊u,eff𝑓𝑢/𝛾M2 , (6.24)

where 𝑊u,eff is effective section modulus, obtained using a reduced thickness 𝜌𝑐𝑡 for class 4 parts and reduced

thickness 𝜌u,haz𝑡 for the HAZ material, whichever is smaller.

Cross-section classification and effective thickness are the same as for the section without transverse weld (Class 3),

so there is no reduction due to local buckling.

The reduction factor for the ultimate strength in HAZ is according to Table 3.1 for EN-AW 6082-T6

𝜌u,haz = 0.60 .

So, the section modulus with allowance for HAZ, due to longitudinal weld and localized transverse weld, is

𝐼u,eff = 𝐼𝑦 − 2𝑏haz𝑡𝑓(1 − 𝜌u,haz)2 (ℎ𝑡

2)

2

− (1 − 𝜌u,haz)2𝑡𝑤(𝑙𝑤 + 2𝑏ℎ𝑎𝑧)3/12 = 6.592 ⋅ 107 mm4

𝑊u,eff =𝐼u,eff⋅2

ℎ= 5.73 ⋅ 105 mm3.

Bending moment resistance at section with transverse weld

Bending moment resistance is according to (6.24):

𝑀u,Rd = 𝑊u,eff𝑓𝑢/𝛾M2 = 142 kNm . (6.24)

This is actually larger than the resistance of the member with longitudinal welds only, which is o,Rd 132 kNmM = .

Therefore, in this case the HAZ in the welds does not reduce the bending moment resistance of the member.

The strength in the weld, according to Table 8.8 for filler metal 5356, is 𝑓𝑤 = 210 MPa, which is larger than the strength

in HAZ, thus not critical.



62

Example 4: Lateral-torsional buckling of member in bi-axes bending and compression

Design data

The beam-column according to Figure 6.5 is loaded by an eccentric axial load, main axis eccentricity at one end and

minor axis eccentricity at both ends. At the top, the load is inserted via a rigid rectangular hollow section beam. There

are simply support at the load points A and C. In this example lateral-torsional buckling is checked according to 6.3.3.2,

formula (6.63) and flexural buckling according to 6.3.3.1, formula (6.59).

l bea

m

ey

D

C

A (B)

NEd

NEdez

tw

b

t f

z

y

r

hwh ht

bw

t1

t 2

t2

b3

b1

b2

D

Figure 6.5: General arrangement, loading and cross-section

- Geometrical data:

Beam length lbeam = 2500 mm

Eccentricity at the top ey = 400 mm, ez = 30 mm

Eccentricity at the bottom ey = 0 mm, ez = 30 mm

- Cross-section data:

Section height h = 200 mm, flange width b = 100 mm

Web thickness tw = 6 mm, flange thickness tf = 9 mm

Fillet radius r = 14 mm



63

Web height 𝑏𝑤 = ℎ − 2𝑡𝑓 − 2𝑟 = 154 mm

Material EN-AW 6082-T6 fo = 260 MPa

Partial safety factor 𝛾M1 = 1.1

- External forces:

Axial compression force 𝑁Ed = 60kN

Bending moment at end C 𝑀y,Ed = 𝑁Ed𝑒𝑦 = 60 ⋅ 0.4 = 24.0kNm

Bending moment at A and C 𝑀z,Ed = 𝑁Ed𝑒𝑧 = 60 ⋅ 0.03 = 1.8kNm

Cross-section classification under axial compression (clause 6.1.4)

The classification according to clause 6.1.4 gives class 2 for the flange and class 4 for the web, which means that in

compression, the overall cross-section class is 4. The resistance is therefore based on the effective cross-section for

the member in compression.

Cross-section classification for y–y axis bending (clause 6.1.4)

In y–y axis bending, the overall cross-section classification is Class 2. The resistance is therefore based on the plastic

section modulus of the member.

Cross-section class under z–z axis bending (clause 6.1.4)

The web is in the neutral axis so, in z–z axis bending, the overall cross-section classification is Class 1. The resistance is

based on the plastic section modulus of the member.

Design resistance for y–y axis bending (clause 6.2.5)

Although the resistance is based on the plastic section modulus, the elastic section modulus is needed to calculate the

shape factors and the exponents in the interaction formulae. If the fillets are omitted, then the elastic section modulus

is

𝑊el,𝑦 = 𝐼𝑦/(ℎ/2) = 2.074 ⋅ 105mm3

Usually the plastic section modulus is not given by the CAD program. Including fillets and using the notations (see

Figure 6.5). Being

ℎ𝑡 = ℎ − 𝑡𝑓 = 191mm and ℎ𝑤 = ℎ − 2𝑡𝑓 = 182mm

it results in

𝑊pl,𝑦 = 𝑏𝑡𝑓ℎ𝑡 +1

4𝑡𝑤ℎ𝑤

2 + 2𝑟2(ℎ𝑤 − 𝑟) − 𝜋𝑟2 [ℎ𝑤 − 2𝑟 (1 −4

3𝜋)]

1

2= 2.364 ⋅ 105mm3.

The shape factor is, therefore:



64

𝛼𝑦 = 𝑊pl,𝑦/𝑊el,𝑦 = 1,140

and the resistance for y–y axis bending

𝑀𝑦,Rd = 𝛼𝑦𝑊el,𝑦𝑓𝑜/𝛾M1 = 1.140 ⋅ 2.074 ⋅ 105 ⋅ 260/1.1 = 55.9kNm

Design resistance for z–z axis bending (clause 6.2.5)

If the fillets are omitted, then (including fillets 𝐼𝑧 = 1.510 ⋅ 106mm4)

𝐼𝑧 =1

12[2𝑡𝑓𝑏3 + ℎ𝑤𝑡𝑤

3 ] = 1.503 ⋅ 106mm4.

The elastic section modulus is 𝑊el,𝑧 = 𝐼𝑧/(𝑏/2) = 3.020 ⋅ 104mm3.

Although the influence of the fillets can be neglected, it is included here

𝑊pl,𝑧 =1

42𝑡𝑓𝑏2 +

1

4ℎ𝑤𝑡𝑤

2 + 2𝑟2(𝑡𝑤 + 𝑟) − 𝜋𝑟2 [𝑡𝑤 + 2𝑟 (1 −4

3𝜋)]

1

2= 4.767 ⋅ 104mm3

The shape factor and the resistance for z–z axis bending are:

𝛼𝑧 = 𝑊pl,𝑧/𝑊el,𝑧 = 1.578

𝑀𝑧,Rd = 𝑓𝑜𝛼𝑧𝑊el,𝑧/𝛾M1 = 11.3kNm.

Axial force resistance for y–y axis buckling (clause 6.3.1)

To calculate the effective cross-section area, the gross cross-section area is first calculated and then the reduction due

to local buckling is made.

𝐴gr = 𝑏ℎ − (𝑏 − 𝑡𝑤) ⋅ (ℎ − 2𝑡𝑓) + 𝑟2(4 − 𝜋) = 3060 mm2

𝐴eff = 𝐴gr − 𝑏𝑤(𝑡𝑤 − 𝜌𝑐𝑡𝑤) = 2969 mm2.

The buckling length is 𝑙cr,y = 2500 mm ,

so, the buckling load and the slenderness are given by

𝑁cr,𝑦 =𝜋2𝐸𝐼𝑦

𝑙cr,𝑦2 = 2293 kN and �̄�𝑦 = √

𝐴eff𝑓𝑜

𝑁cr,𝑦= 0.580 (6.51)

The reduction factor for flexural buckling with 0.2 = and 0 0.1 = , from Table 6.6 for Buckling Class A, is 𝜒𝑦 = 0.880.

Buckling resistance according to (6.49) for no welds and leaving 𝜔𝑥 is

𝑁𝑦,b,Rd = 𝜒𝑦𝑓𝑜𝐴eff/𝛾M1 = 618 kN. (6.49)

Cross-section resistance is needed in the interaction formulae

𝑁Rd = 𝑓𝑜𝐴eff/𝛾M1 = 702 kN.

Axial force resistance for z–z axis buckling (clause 6.3.1)

The buckling length is 𝑙cr,y = 2520 mm. The buckling resistance according to (6.49), based on 𝜒𝑧 = 0.195 is given by



65

𝑁𝑧,b,Rd = 𝜒𝑧𝐴eff𝑓𝑜/𝛾M1 = 137 kN. (6.49)

Lateral-torsional buckling of beam in bending (clause 6.3.2.1)

The elastic lateral-torsional buckling load is found in Annex I. The torsion constant is found in Annex J and the warping

constant in Annex J, Figure J.2 case 5a, which gives:

𝐼𝑤 = (ℎ − 𝑡𝑓)2𝐼𝑧/4 = 1912 ⋅ 1.51 ⋅ 106/4 = 1.377 ⋅ 1010 mm6

The last term in (J.1) is not needed so the torsion constant, including the fillets, is

𝐼𝑡 = ∑ 𝑏𝑡3/3 − 0.105 ∑ 𝑡4 + ∑ 𝑎𝐷4 (J1.a)

where D is found in Annex G, Figure J.1 case 2:

𝐷 = ((𝛿 + 1)2 + (𝛿 + 0.25𝑡1/𝑡2)𝑡1/𝑡2)(𝑡2/(2𝛿 + 1))

With 1 w 6 mmt t= = and 2 f 9 mmt t= = then 2/ 14 / 9 1.556r t = = = (see Figure 6.5)

and 𝛼 =(0.10𝛿+0.15)𝑡1

𝑡2= 0.204 . Therefore:

𝐷 = 16.8 mm.

Now, from equation (J1.a), the value of tI , for two flanges with fillets, is 𝐼𝑡 = 9.402 ⋅ 104 mm4.

It is important to notice that:

if the fillets are omitted then 𝑰𝒕 = 𝟔. 𝟐𝟒 ⋅ 𝟏𝟎𝟒 mm𝟒; by adding just 5% material, the torsion constant is increased

51% !

The elastic critical moment for lateral-torsional buckling is given by the general formula

𝑀cr = 𝜇cr𝜋√𝐸𝐼𝑧𝐺𝐼𝑡

𝐿 (I.2)

where the relative non-dimensional critical moment cr is found in Annex I.

Without presenting it in detail, their values are 𝜇cr = 2.272 and 𝑀cr = 46.8 kNm.

The relative slenderness �̅�LT and the bending moment resistance is found in 6.3.2, which gives

𝑀𝑦,b,Rd = 37.7 kNm.

Interaction formulae

Both flexural buckling according to clause 6.3.3.1 and lateral-torsional buckling according to clause 6.3.3.2 need to be

checked, see 6.3.3.2(2).

For major axis (y–axis) bending

y

y,EdEd

y,RdRd

1.00x

y

MN +

N M

(6.59)

For lateral-torsional buckling



66

zzzy,EdxLT z,EdEd

y,Rd z,RdRd LT

1.00x

z

M MN + +

N M M

(6.63)

To shorten the formulae, the following notations are introduced

𝐾0 =𝑁Ed

𝑁Rd=

60

702= 0.0855 and 𝐵0 =

𝑀𝑦,Ed

𝑀𝑦,Rd=

24

55.9= 0.430.

The exponents 𝜂𝑦, 𝜂𝑧 and 𝛿𝑧 in the interaction formulae are given in 6.3.3.1(1) and 6.3.3.2(1).

Conservatively, all exponents may be taken as 0.8. To show the complete procedure, the formulae for the exponents

are shown.

𝜂𝑦 = 𝜒𝑦min{𝛼𝑦2; 1,56)} but 𝜂𝑦 ≥ 1.0 → 𝜂𝑦 = 1.14

𝜂𝑧 = 𝜒𝑧min{𝛼𝑧2; 1,56)} but 𝜂𝑧 ≥ 1.0 → 𝜂𝑧 = 0.80

𝛽𝑧 = 𝜒𝑧min{𝛼𝑧2; 1,56)} but 𝛽𝑧 ≥ 1.0 → 𝛽𝑧 = 1.56

𝛿𝑧 = 𝜒𝑧min{𝛼𝑧2; 1,56} but 𝛿𝑧 ≥ 0,8 → 𝛿𝑧 = 0.80

Lateral-torsional buckling check (clause 6.3.3.2)

The formula for defining the design section is according to 6.3.3.5(2)

𝑐𝑜𝑠 (𝑥𝑠𝜋

𝑙𝑐) =

(𝑀Ed,1−𝑀Ed,2)

𝑀Rd⋅

𝑁Rd

𝑁Ed⋅

1

𝜋(1/𝜒−1) , but 0s x (6.71)

where 𝑙𝑐 = 𝑙cr,𝑧, 𝑀Ed,1 = 𝑀𝑦,Ed, 𝑀Ed,2 = 𝜓𝑦𝑀𝑦,Ed = 0 and the ratio between the moments at the ends is 𝜓𝑦 = 0.

Formula (6.71) can now be evaluated

𝑐𝑜𝑠 (𝑥𝑠𝜋

𝑙cr,𝑧) =

𝐵0

𝐾0

(1−0)

𝜋(1/𝜒𝑧−1)= 0.387 but 0s x

𝑥𝑠𝜋

𝑙cr,𝑧 = acos(0.387) = 1.173 rad and 𝑥𝑠 = 1.173 ⋅ 2500/𝜋 = 934 mm.

The interaction formulae 𝜔𝑥 and 𝜔𝑥LT according to 6.3.3.5(1) are

sx

c

1/ (1 ) sinx

= l

+ −

(B.1)

sxLT LT LT

c

1/ (1 ) sinx

= l

+ −

(6.70)

The three terms in the interaction formula (6.63) can be evaluated separately.



67

zc

0 0 s

cr,

(1 ) sin 0.491z z zzz z z

K K xK

l

= = + − =

zz

0 s sLT LT

cr,yxLT LT LT c

1 (1 ) (1 )sin 0.229xy y

B B x xB

ll

= = − − + − =

z 0.8,Ed

,Rd

1.800.231

11.3

zz

z

MB

M

= = =

Being

𝐾𝑧 + 𝐵𝑦 + 𝐵𝑧 = 0.491 + 0.229 + 0.231 = 0.951 < 1,

lateral-torsional buckling check is accepted.

For lateral-torsional buckling, the design section is close to the centre of the beam due to large second order bending

moment (Figure 6.6 a). Figure 6.6 shows the behavioural differences between lateral-torsional buckling (a) and flexural

buckling (b).

Kz By Bz Ky By

xs

(a) Lateral-torsional buckling (b) Flexural buckling

Figure 6.6: K- and B-diagram and design sections (dash-dotted)

Flexural buckling check (6.3.3.1)

The formula (6.71) for defining the design section according to 6.3.3.5(2) for y–y–axis buckling is evaluated as for z-z-

axis buckling, except that 𝑙cr,z is replaced by 𝑙cr,y and 𝜒𝑧 is replaced by 𝜒𝑦. As the reduction factor 𝜒𝑦 is close to 1.0

(0.880) the top section will be the design section. See Figure 6.6 (b).

Formula (6.59) should then be checked with 𝜂𝑧 = 𝜂𝑦 and 𝜔𝑥 = 𝜒𝑦 .

Being

𝐾𝑦 + 𝐵𝑦 = 0.060 + 0.430 = 0.490 < 1,



68

flexural buckling check is accepted.

Example 5: Welded connection between diagonal and chord member Design data

Referring to Figure 6.7, calculate the tensile resistance of a welded connection of an L-diagonal into a chord member. The material in the diagonal and chord is EN-AW 6005A, with ultimate strength 𝑓𝑢 = 270 MPa and 𝜌u,haz = 0.61. Filler

metal is 5356, having 𝑓𝑤 = 180 MPa according to Table 8.8. The angle between the diagonal and the chord is 0 42 =

. The distance from edge to centre of gravity of the angle section 57 mm×6 mm is 1 17 mme = and thickness 1 6 mmt =

.

e 1

a3

a4

a2

a1

l1

l4

l2 β0

FEd

e 2

l 3

t 1

b

A

A

A-A

e1

Δa2

yt 1

t1 ρ

u,haz

y

f u

2f u z

1

2

3

4

abhaz

Figure 6.7: Connection of diagonal into chord of build-up member

The resistance of the four welds is derived with formula (8.31) and the corresponding values are given in Table 6.1, where also the moment due to the eccentricity is calculated. By reducing the weld 1 to 75 mm, the moment value is practically 0. The resistance of the oblique weld 4 is derived from formula (8.31) and the stresses according to Figure 6.8. The result is a factor

𝑓(𝛽) = (2 sin2 𝛽 + 3 cos2 𝛽)−1 for 𝑓w/𝛾Mw to get the strength of the weld, where 𝛽 = 𝛽0 in Figure 6.8.

a

τ

σ

Fsinβ

L

a β

Fsinβ

Fcosβ

F

a) b)

Figure 6.8: Stresses in oblique fillet weld



69

In practice the welds 3 and 4 are extended over the whole width of the angle section. Alternatively weld 2 is completed

with a weld 2a (a) and the length of weld 1 is increased.

Weld L /mm A /mm 𝛽0 E /mm fw/Mw MPa f() FRd /kN Me /kNm

1 75 3 0 17 144 0.577 18,7 0,318

2 32 3 0 -40 144 0.577 8,0 -0,319

3 34 3 90 0 144 0.707 10,4 0

4 51 3 42 0 144 0.626 13,8 0

Sum 50.8 -0.001

Table 6.1: Weld data

From Table 6.1 the sum of the resistance of the welds is 𝐹Rdw = 50.8 kN. The resistance in the heat affected zone HAZ is based on the net section area of the angle section, considering HAZ

extended all over the flange in the joint plane and for hazb in the perpendicular flange, being the extent 𝑏haz = 25 mm

according to clause 6.1.6.3 and the reduction factor 𝜌u,haz = 0.61. The net section, according to 6.2.3, is then

𝐴net = 𝑡(𝑏 − 𝑏haz) + 𝑡(𝑏 + 𝑏haz − 𝑡)𝜌u,haz = 6 ⋅ (57 − 25) + 6 ⋅ (57 + 25 − 6) ⋅ 0.61 = 470 mm2.

It is supposed that the tension force is acting in the plane of the joint. Then a bending moment is acting on the angle section, which is carried by plastic distribution of stresses in the cross-section according to Figure 6.7. The compression part z is derived in such a way that the moment in the plane of the joint (mid of angle leg) is zero (note 2tz on the right end side of the equation). Then

𝑡(𝑏 − 𝑡/2)2/2 − 𝑡(𝑏haz − 𝑡/2)2/2 ⋅ (1 − 𝜌u,haz) = 2𝑡𝑧(𝑏 − 𝑧/2)

from which

𝑧 = 𝑏 − √𝑏2 − (𝑏 − 𝑡/2)2/2 + (𝑏haz − 𝑡/2)2(1 − 𝜌u,haz)/2 = 13.6 mm.

The design resistance is therefore:

𝐹Rd = 𝐴net

𝑓𝑢

𝛾M2− 𝑡𝑧

2𝑓𝑢

𝛾M2= 470 ⋅

270

1.25− 6 ⋅ 13.6 ⋅

2 ⋅ 270

1.25= 66.3 kN

which is larger than the resistance of the welds 𝐹Rdw = 50.8 kN (Table 6.1).

Example 6: Resistance of equivalent T-stub

Design data

Calculate the resistance of a T-sub corresponding to a pair of bolts within c according to Figure 6.9.

Material properties and dimensions are the following:

EN-AW 6005A, Table 3.2a: o 200 MPaf = and u 250 MPaf =

HAZ properties: o,haz 115 MPaf = and u,haz 165 MPaf =

Thickness of flange plate: f 15 mmt =

Lever arm: 20 mmg =

Edge distance: min 20 mme =



70

Bolt distance: 30 mmc =

Steel bolt 8.8: 10 mmd = .

emin

g

a

t f

l e

ff

g eeee g0.8a 2 (or 0.8r)

c

1 2

1 2

Figure 6.9: Equivalent T-stub

According to 8.10(2):

Ultimate strain: u 8 % = from Table 3.2a

Elastic strain: oo

2000.00286

70000

f

E = = =

Strain relation: ( ) ( )

u o

u o

1.5 0.08 1.5 0.002860.6543

1.5 1.5 0.08 0.00286

− − = = =

− − (B.9)

Stress relation: o u o

u o

1 200 250 2001 1 0.6543 0.931

250 200

f f f

k f f

− − = + = + =

(B.8)

Edge distance: minmin( ,1.25 ) 20 mmee e g= =

8.8 steel bolt: 𝑑 = 10 mm, 𝑑0 = 𝑑 + 1 mm = 11 mm, y 640 MPaf = and ub 800 MPaf =

Yield strength: s yo

M2

58 6400.9 0.9 26.7 kN

1.25

A fB

= = = (B.10)

Ultimate strength: s buu

M2

58 8000.9 0.9 33.4 kN

1.25

A fB

= = = (= t.RdF ) (8.17)

Effective length 2: eff,2 30 mml =

Effective length 1: eff,1 eff,2 o 30 11 19 mml l d= − = − =

Moment resistances in section 1 and 2:



71

2 2u,1 f eff,1 u

M2

1 1 1 1 1( ) 15 19 250 0.931 0.199 kNm

4 4 1.25M t l f

k = = = (B.5)

2 2u,2 f eff,2 u,haz

M2

1 1 1 1 1( ) 15 30 165 0.931 0.207 kNm

4 4 1.25M t l f

k = = = (B.6)

2 2o,2 f eff,2 o,haz

M1

1 1 1 1( ) 15 30 115 0.176 kNm

4 4 1.1M t l f

= = = (B.7)

Q Q

(Mu)w

(Mu)b

M

Q Q

Mo<M <Mu

M

Q Q

Mu

M

Bo Bo Bu Bu Bu Bu

Fu Fu Fu Fu

Figure 6.10: Failure modes

If there are no welds in section 2, replace u,hazf with uf and o,hazf with of .

Mode 1: Flange failure by developing two hardening plastic hinges at the web-to-flange connection (w)

(= u,2M ) and two at the bolt location (b) (= u,1M ) (for g and ee , see Figure 6.9)

u,2 w u,1 bu,Rd

2( ) 2( ) 2 207 2 19940.6 kN

20

M MF

g

+ + = = = (B.1)

Mode 2a: Flange failure by developing two hardening plastic hinges with bolt forces at the elastic limit

u,2 ou.Rd

2 2 236 20 2 26.738.5 kN

20 20e

M n BF

g e

+ + = = =

+ +

(B.2)

Mode 2b: Bolt failure with yielding of the flange at the elastic limit

o,2 uu,Rd

2 2 176 20 2 33.442.2 kN

20 20e

M n BF

g e

+ + = = =

+ +

(B.3)

Mode 3: Bolt failure

u,Rd u 2 33.4 66.8 kNF B= = = (B.4)

Design resistance is the smallest value of the four failure modes

u,Rd 38.5 kNF = for Mode 2a.



72

Chapter 7 – Execution of aluminium structures

A milestone for the harmonisation of the marketing of construction products in the EU was the CPD-Construction

Products Directive (EEC) No 89/106, issued 1989 and then replaced in 2011 by the CPR-Construction Products

Regulation (EU) No 305/2011. In the framework of the current legislative framework (the CPR), a set of harmonised

standards are currently in use to assess and declare the performance of metallic products and ancillaries. Among these

we have:

• EN 1090-1:2009+A1:2011 Execution of steel structures and aluminium structures - Part 1: Requirements for

conformity assessment of structural components; supported by:

o EN 1090-3:2019 Execution of steel structures and aluminium structures - Part 3: Technical

requirements for aluminium structures; 2008, revised and amended 2019;

o EN 1090-5:2017 Execution of steel structures and aluminium structures - Part 5: Technical

requirements for cold-formed structural aluminium elements and cold-formed structures for roof,

ceiling, floor and wall applications;

• EN 15088:2005 Aluminium and aluminium alloys - Structural products for construction works - Technical

conditions for inspection and delivery.

The implementation of EN 1090-1 had always been one of the biggest challenges for the manufacturers of aluminium

(and steel) structures since, in many countries, manufacturers were not accustomed to follow strict production rules

under the control of newly established control authority (the so-called notified bodies).

Concerning the manufacturing of aluminium structures or aluminium structural components, the manufacturer has

generally to follow and fulfil the provisions laid down in EN 1090-1, while EN 1090-3 specifies requirements for the

execution of aluminium structural components and structures made from rolled sheet, strip and plate, extrusions, cold

drawn rod, bar and tube, forgings, castings.

Annex A of EN 1999-1-1 defines four execution classes (EXC), i.e. a product characteristic linked to the manufacturing of a component which defines the engineering effort required to realise specific project parameters. EXC2 is the most common specification; complexity increases as the number rises.

EN 1999-1-1 helps for the determination of the Execution Class:

Consequence class CC1 CC2 CC3

Service category SC1 SC2 SC1 SC2 SC1 SC2

Production

category

PC1 EXC1 EXC1 EXC2 EXC3 EXC3a) EXC3 a)

PC2 EXC1 EXC2 EXC2 EXC3 EXC3 a) EXC4 a) EXC4 should be applied to special structures or structures with extreme consequences of a structural failure in

the indicated categories as required by national provisions.

Where:

with Service Category differentiation is done between static design (SC1) and fatigue design (SC2)

with Production Category differentiation is done between not welded (PC1) and welded components (PC2)

with Consequence Class is meant the provisions defined in EN 1990 Table B.1

Table 7.1: Determination of execution class (Table A.3 in EN 1999-1-1)



73

Consequences class Description Example of buildings and civil

engineering works

CC3 High consequence for loss of human

life, or economic, social or

environmental consequence very great.

Grandstands, public buildings where

consequences of failures are high

(e.g. a concert hall)

CC2 Medium consequence for loss of human

life, or economic, social or

environmental consequence

considerable.

Residential and office buildings,

public buildings where

consequences of failure are medium

(e.g. an office building)

CC1 Low consequence for loss of human life,

or economic, social or environmental

consequence small or negligible.

Agricultural buildings where people

do not normally enter (e.g. storage

buildings), greenhouses

Table 7.2: Definition of consequences classes (Table B1 in EN 1990)

In order to avoid the choice of unnecessarily high execution classes by designers, some countries have decided to

define individually the applicable EXC depending of the kind of the structure, e.g. by listed of structural examples in

the National Application Documents (NAD).

The consequences of the different EXCs defined by the designing engineer or the customer for the manufacturing

consist essentially in different requirements concerning the amount of testing and documentation. But also,

consequences concerning the personnel exist and their economical aspect may not be underestimated, see the Table

7.3 about the required technical knowledge of welding coordination personnel.

Table 7.3: Required technical knowledge of welding coordination personnel (Table 9 in EN 1090-3)



74

Chapter 8 - Maintenance

Seeking for an almost lifelong maintenance-free material, aluminium is the material of choice. Its durability combined

with its resistant coating and typical finishes, such as anodization, makes aluminium structures extremely easy to

maintain. Maintenance work for aluminium products is almost unnecessary, due to the excellent corrosion behaviour

of this element. While protective measures might concern those elements that are used to assemble structural

members (e.g. bolts), most aluminium structures can remain unprotected if the environmental conditions allow that.

Nevertheless, we see more and more structures (e.g. pedestrian bridges) which are coated in many attractive colours,

although this is not strictly necessary to protect from corrosion but adds aesthetic value to the structure itself. Coating

of aluminium with organic materials is a means to improve the attractiveness of aluminium-based structural solutions.

The durability of organic coatings on aluminium is excellent. Uniform colours as well as personalised designs or

patterns can be applied to it.

Another way of treating aluminium surfaces is done through a very specific process called “anodization”. In case of

continuous anodization, this process allows to create a stable oxide layer with a controlled thickness up to 25 μm, on

top of a natural oxide surface layer of a few nm. The stable oxide layer guarantees additional resistance to UV,

scratching and corrosion of the product. Indeed, this additional layer is very resistant against weathering agents and

often appreciated for its decorative versatility (see Figure 8.1). Thicker anodized protective layers can be achieved

through batch anodization.

Figure 8.1: Example of pallet of colours from anodization process (Coil, Aloxide products)

As structural materials are often exposed to outside weather conditions, soiling can ruin the original decorative

appearance of the surfaces. At the same time soiling increases the risk of corrosion. Therefore, cleaning at least once

a year ,using neutral cleaning agents, is recommended to preserve the original look. Acids or alkaline cleaning agents

should be avoided while neutral solutions (pH 5 to 8) in combinations with mechanical cleaning are to be privileged.

Organic coatings may be removed by organic solvents, which make no harm to aluminium.

In general, it is recommended to visually inspect structures that are not frequently used or checked, to verify that no

major alterations have taken place, such as damaging parts of the structure by accident, vandalism or deliberately by

unauthorized persons. The state of coatings and possible deposition of dust, soil or leaves are to be checked as they

might influence the appearance of the structure or create corrosion risks.



75

Structures that are exposed to cyclic loads are prone to fatigue. Mandatory regular checks are necessary, as fatigue

fractures can occur under much lower stress compared to static load conditions. EN 1999-1-3 distinguishes two cases:

Safe life method/principle

This method is applied in case the structure has been designed, or a priori can be assumed, to perform safely

for a specific period of time with an acceptable small probability of failure by fatigue cracking.

Damage tolerant design/method

This method can be applied in case the structure is designed damage tolerant, which means the structure

withstands local defects safely until maintenance work is carried out.

For the safe life method, a systematic inspection for fatigue cracks is negligible, which is why this method is

typically applied where inspections are generally considered as not possible. In case of an applied damage

tolerant design, a systematic inspection system of the structure is an inherent part of this method. Critical spots

must be checked with respect to fatigue cracks and measures must be taken to repair or to replace the

respective component. Details about the frequency, the beginning of inspections in combination with different

safety factors and for different consequence classes are given in EN 1999-1-3.

In order to support the decision what method is to be preferred, a Note in EN 1999-1-3 (i.e. 2.2.2(1)) informs that “the

damage tolerant design method may be suitable for application where a safe life assessment shows that fatigue has a

significant effect on design economy and where a higher risk of fatigue cracking during the design life may be justified

than is permitted using safe life design principles.” Such method is intended to result in the same reliability level as

obtained by using the method of safe life design.

For engineering structures in connection with roads (e.g. bridges, traffic sign structures, etc.) a higher frequency of

inspections is recommended as accidents can happen at any time. However, this does not only concern aluminium. In

this case, regulations about the frequency of inspections given by national or local authorities (in some cases even by

insurance companies) are to be followed.



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Chapter 9 – Sustainability of aluminium structures

9.1.The aluminium cycle

Aluminium is a material that shows its value at every stage of its life cycle, from production till the end of use.

Aluminium can rightfully claim to be a material with "permanent" characteristics or properties, meaning the inherent

properties do not change during use and following repeated recycling into new products. Obviously, used aluminium

has to be collected and sorted properly to make it available for its next use phase.

Figure 9.1: the aluminium cycle

A way to acquaint environmental information of aluminium products is by the means of so-called Environmental

Product Declarations (EPD). An independently verified and registered document that communicates transparent and

comparable information about the environmental life-cycle impact of products.

9.2. Metal sourcing More than half of the aluminium currently produced in the European Union originates from recycled raw materials,

and this trend is increasing. As the energy required to recycle aluminium is about 5% of that needed for primary

production, the ecological benefits of recycling are obvious. Due to the long lifespan of buildings and transport vehicles,

the available quantity of end-of-life aluminium scrap today is limited to what was put on the market many years ago.

This volume being much less than the current demand, the missing quantity needs to be supplied by the primary

aluminium industry. Bauxite, the ore from which primary aluminium is produced, originates mainly from Australia,

Brazil, West Africa and the West Indies, as well as from other tropical and sub-tropical regions. Rehabilitation of existing

mining areas balances out the commissioning of new mining areas. 98% of mines have rehabilitation plans, and the

area returned to native forests is expected to be higher than the original vegetation before mining2.

2 4th Sustainable Bauxite Mining Report. International Aluminium Institute - 2008



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Primary aluminium is obtained by the electrolysis of alumina (aluminium oxide) that is extracted from bauxite. Total

greenhouse gas emissions from European aluminium were reduced by 45% between 1990 and 2005.

9.3. Transformation

Aluminium flat products are obtained through the rolling process, whereby large aluminium slabs are fed into rolling

mills that turn aluminium into sheets of various thicknesses. The process normally begins with a hot rolling method,

moving the block back and forth through a reducing roller. Final rolling is a cold roll process, and the sheet can be

reduced to a thickness of 0.15 mm. The sheet can be further thinned into foil of a thickness of 0.007 mm. Further

information of the availability of sheets and plates for structural purposes can be found in chapter 3.9.1.

Aluminium is one of the few metals that can be casted in all metal casting processes. The most common methods

include die casting, permanent mould casting and sand casting. Castings can be made to virtually any size. Thus, the

material has little restrictions in design and is of great advantage for architects.

Aluminium profiles are obtained through the extrusion process. A hot cylindrical billet of aluminium is pushed through

a shaped die (for more information, refer to chapter 3.9.2). The ease with which aluminium alloys can be extruded into

complex shapes allows the designer to “put metal exactly where it is needed”, and also to introduce multi-functional

features. In construction, aluminium extrusions are not only used for structural purposes, but are also commonly used

in commercial and domestic buildings for windows, doors and curtain wall frame systems and many other applications.

9.4. Use phase

Aluminium is highly appreciated for its very long in-service life, low maintenance and other assets like light weight,

corrosion resistance and functionality. These assets are explained more in detail in chapters 4 and 8.

9.5. Deconstruction and collection

A study by Delft University of Technology revealed aluminium’s considerable end-of-life recovery rate in the building

sector. Aluminium collection rates taken from a large sample of commercial and residential buildings in six European

countries were found to be above 92% (on average 96%), demonstrating the value and preservation of the material at

the end of the aluminium product life cycle.

9.6 Recycling

The high intrinsic value of aluminium is a major economic incentive for its recycling. Indeed, aluminium scrap can be

repeatedly recycled without any loss of value or properties. Furthermore, the energy required is a mere fraction of

that needed for primary production, often as little as 5%, yielding obvious ecological benefits.

In many instances, aluminium is combined with other materials such as steel or plastics. Mostly they are mechanically

separated from aluminium before being molten: shredding followed by eddy current and sink-float separation.

Aluminium can then be melted either by remelters or refiners.

• Remelters mainly process wrought alloy scrap. They produce extrusion billets or rolling slabs.

• Refiners melt all kinds of scrap, including mixed alloys and soiled scrap. They mainly produce casting alloys

for foundries.



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As technology evolves, a growing number of remelters are now able to process coated and polymer containing scraps

with no or limited preparation processes. One solution is the use of a two-chamber furnace: finishes to the aluminium

(e.g. coating) are burnt away in the first chamber and gas emissions are collected in efficient fume capture equipment

while aluminium heating mainly takes place in the second chamber. Alternatively, plants using pyrolysis technology

use the organic particles attached to the aluminium scrap as fuel for the pyrolysis process that takes place in rotating

drums while the heat burns away the organic material off the metal.

Liquid aluminium can then be transported directly to foundries, casted into ingots, extrusion billets or rolling slabs

ready to get reused. Consequently, the life cycle of an aluminium product is not the traditional “cradle-to-grave”

sequence, but rather “cradle-to-cradle”.

Chapter 10 - Applied examples of Aluminium Structures All the examples of real structures shown here represent relevant cases where the aluminium has been selected

because it has been demonstrated that this solution was more competitive than the one in steel. In all cases, the basic

pre-requisites already defined in Chapter 4 have been fundamental for deciding the aluminium choice.

When the incidence of the structural weight is fundamental, the utilization of the aluminium can represent a valid

alternative to steel. In addition, the complete absence of maintenance, due to corrosion resistance, increases the

advantages for those structures situated in humid environments.

10.1. Lattice space structures Several applications of lattice space structures can be found in South America (Brazil, Colombia, Ecuador). The

historical background in this field is represented by a very spectacular space structure which has been erected for the

Interamerican Exhibition Center of San Paulo in Brazil in 1969 (Fig. 10.1). This structure covers an area of about 67600

m2 with a mesh 60x60 m. The depth of the lattice layer is 2,36 m. It was entirely site-bolted on the ground and after

lifted at the final level of 14 m by means of 25 cranes located in the corners of the mesh, in the position of the actual

supports. The weight of the lattice structure was 16 kg/m2; the number of bars was 56820 and their total length one

after another was 300 km. The erection time was extraordinary quick (27 hours!), by using a number of 550000 bolts

in 13724 nodes. The materials were: aluminium alloys of 6063 and 6351 series T6 for cylindrical bars; Al 99,5 for

trapezoidal sheeting and galvanized steel bolts for connections. Very similar is the case of the International Congress

Centre in Rio de Janeiro, where the same mesh 60x60 m has been used, covering in total 33000 m2 (Fig.10.2).

Among many different applications, mention can be given to lattice system covered by aluminium sheeting for roofing the Sport Hall of Quito, Ecuador (Fig. 10.3) and to the lattice vault for roofing the swimming pool of the Country Clubs of Hatogrande and Guymaral in Bogotá, Colombia (Fig. 10.4).

10.2 Reticulated domes The reticulated domes represent the most challenging application of aluminium alloys in the structural field, allowing

the realisation of important constructions (sporting houses, exhibition centres, congress halls, auditoriums, etc). These

applications are very interesting for the rapidity of erection, the connection systems and the remarkable dimensions.

The first applications of this kind of structures were: the “Dome of Discovery” erected in London for the South Bank

Exhibition during the Festival of Britain (1951), composed by three directional reticulated arches, with a diameter of

110 m and 24 kg/m2 weight (Fig.10.5) and the geodetic dome erected for covering the “Palais des Sports” in Paris, by

using the Kaiser Aluminium system with 61 m diameter and 20 m height (1959) (Fig.10.6). Both were like prototypes

in their field, being the largest and the first, respectively.



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10.3 Geodetic domes More recently, interesting structural systems for geodetic domes made of aluminium have been set-up in U.S.A. The

Tem-cor, Conservatex and the Geometrica systems are used both for roofing industrial plants with ecological purposes

(Fig. 10.7) and for large roofing public buildings (Fig.10.8). A famous application in USA was the “Spruce Goose” dome

in Long Beach (California), which contained an airplane claiming the largest wingspan of any aircraft in history and

being still the largest flying boat ever made in 1947. Since 2009, it was the largest dome in the World with a diameter

of 126 meters (Fig. 10.9).

A significant application of geodetic dome has been done in the restauration of the Museum of “Mercati Traianei” in

Rome (Fig. 10.10), by using a special aluminium bar-to-node system, called “geo-system” (designer F.M. Mazzolani).

Many geodetic domes are used for industrial applications, like for roofing coal storage plants (Fig. 10.11). The

transformation into coal of the thermo-electrical power plant of ENEL in Torrevaldaliga North (Civitavecchia) required

a complete change in handling and storing systems, as the fuel is passed from liquid (oil) to solid (coal). The prevention

of the dispersion of dust into the environment resulted in a total confinement system for handling the coal from the

harbour to the boiler through conveyor belt network. For this purpose, two geodetic domes with the diameter of 144

meters have been designed and built by using the MERO system (Fig. 10.12, designer F.M. Mazzolani). Today, they are

the largest aluminium domes in the World and in 2012 they received the European Aluminium Award with the

following statement of the jury:

“The jury was admiring the overall quality of the structure, which shows that aluminium is a preferable choice for such

large constructions. This dome is both an innovative, environmentally friendly and aesthetic solution for coal storage”.

10.4 Special structures There are special structures having the function to support fixed elements, the prevalent dimension being horizontal

(i.e. portal frames for traffic sign, Fig. 10.13) or vertical (i.e. antennas, lighting towers and electrical transmission, Fig.

10.14). For these structures, the elimination of maintenance represents a fundamental prerequisite. At the same time,

the extrusion process can improve the geometrical properties of cross-sections in such a way to obtain the minimum

weight and the highest structural efficiency. In addition, the lightweight of aluminium allows prefabricated systems,

very easy for transportation and erection, giving rise to competitive solutions in comparison with other materials.

Many towers for electrical transmission lines have been erected in Europe (Fig.10. 14). Two important aluminium

towers have been erected in Naples. The first is the tower for parabolic antennas of the Electrical Department of Naples

erected in 1986 (Fig. 10.15, designer F.M. Mazzolani). This design received the international award “Hundred Years of

Aluminium”. The reason of the aluminium choice was basically due to lightness (the tower has been erected on the

top of an existing reinforced concrete staircase) and corrosion resistance (no problems of maintenance). Its height is

35 m from the top of the staircase (in total 50 m about). It is composed by a cylinder 1800 mm internal diameter and

20 mm thickness. The fabrication was shop-welded, by dividing the total height in three parts, which were field-bolted

during the erection.

The second example is the “Information Tower” near the football stadium in Naples, which has been equipped by

antennas and screens in order to follow from out-side the stadium games (Fig. 10.16, designer F.M Mazzolani). It was

built for the Score International Games of 1990.

A field, where the aluminium properties play a determinant role, is the one of the hydraulic applications (pipelines,

reservoir). The rotating crane bridges for large settling circular pools in water sewage treatment plants is a typical case.

In particular, the corrosion resistance allows to eliminate any protection also in presence of corrosive environment,



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while the lightness corresponds to energy saving during the operating phases of the plant. Eight rotating crane bridges

have been erected in the Po Sangone sewage plant of Torino (Italy) in 1985 (Fig. 10.17, designer F.M. Mazzolani).

10.5 Off-shore applications It seems important to underline that nowadays the offshore applications can be considered the main future trend for

aluminium alloys. In fact, they offer to this industry enormous benefits under form of cost savings, ease of fabrication

and proven performance in hostile environments (Fig. 10.18). Stair towers, mezzanine flooring, access platforms,

walkways, gangways, bridges, towers and cable ladder systems can all be constructed in pre-fabricated units for simple

assembly offshore or at the fabrication yard (Fig.10.19). Mobility and ease of installation are maintained even for large

structural elements, such as link bridges and telescopic bridges. Helidecks have been made by using aluminium alloy

since the early seventies, so they have now a fully tried experience. Moreover, they are designed to be modular and

bolted connections, allowing quick erection, easy shipping and handling. In addition, they offer weight reduction of up

to 70% over steel, meeting the highest safety standards and proving up to 12% cost saving (Fig. 10.20). Complete crew

quarters and utilities modules, from large purpose-built modules to flexible prefabricated units, have been recently

developed. The modules may be used singly or assembled in group to form multi-story complexes, linked by central

transverse corridors and stair towers (Fig. 10.21).

10.6 Bridges All kind of structural schemes typical for steel bridges have been experienced in aluminium alloys. Also, the technology

based on the use of composite structures made of aluminium beams and concrete decks has been applied in some

bridges built since the sixties in USA and later in France.

The Arvida Bridge in Quebec, Canada (1950), the challenging prototype of motorway bridge made of aluminium alloy,

was built according to the Maillart’s scheme with a total span of 150 m, an arch of 87 m of span and total weight of

200000 kg (Fig.10.22). Other motorway bridges have been built in France and in The Netherlands (Fig.10.23).

The footbridge is a structural typology where the aluminium alloys are successfully employed; examples of aluminium

foot bridges can be easily found all over the world (Fig. 10.24).

Owing to the low live load, additional advantages due to lightness are evident in case of moving bridges, which first

example was the moving bridge at the entrance of the Aberdeen harbour in Scotland (Fig. 10.25). More simple and

easy to manage are the moving aluminium bridges for pedestrians (Fig.10.26).

Prototypes for new floating bridges, composed by floating units, have been recently validated and built so to allow

crossing of water straits (Fig.10.27).

A new important field of application is the one of military bridges in which lightness and corrosion resistance play a

fundamental role. At present, it is possible to reach 40 meters of span with prefabricated elements easy to transport

and to erect. The main applications have been developed in Great Britain, Germany, Sweden and Canada (Fig.10.28).

A lightweight system for replacing damaged concrete bridge decks has been developed and used in Sweden, based on

an orthotropic plate of aluminium hollow extrusions (Fig.10.29). This solution can be in many cases very competitive

as an alternative to the conventional solutions. When it substitutes a concrete deck, a reduction in weight is about 10

times, going from 600 to 700 kg/square meter to 50 o 70 kg/square meter. This weight reduction has made it possible

to increase the service load and use the existing foundations without any consolidation operation.

During the seventies, a rehabilitation program for ancient suspension bridges of 19th Century have been developed in

France. Aluminium alloy deck and girders have been successfully applied in the refurbishment of three bridges: the



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Montmerle (Fig.10.30) and the Trevoux (Fig.10.31) bridges on the Soane river with two bays of 80 m; the Groslée

bridge on the Rhône river with a single bay of 174 m (Fig.10.32).

More recently, in the context of a wider rehabilitation programme of the zone, the structural retrofit project has been

done for the oldest Italian suspension bridge, the “Real Ferdinando” on the Garigliano river, which was built in 1832

and was destroyed in 1944 during the World War II by the German army in retreat. The restoration criteria were chosen

in order to satisfy several requirements: a) historical preservation, b) stiffening of the deck, c) respect of the modern

design code provisions, d) adoption of innovative technologies and materials. Comparing other materials, the use of

aluminium alloy has been selected for the main and transversal girders of the new deck, allowing the conservation of

the original geometrical configuration and appearance (Fig.10.33, designer F.M. Mazzolani).

Aluminium has proven to be the material of choice also for the BITSCHNAU toolbridge system, which was developed

to take advantage of the main characteristic of the material, such as low maintenance needs, resistance to corrosion,

very long operational life, persistent and high-quality sustainability and best price-performance ratio. The system is

made with sea water-resistant aluminium alloy, whose surface can be decorated through anodizing or varnish coating.

This type of special bearing constructions (Fig 10.34 and 10.35) make it possible to equalize level differences of

abutment up to 20mm and are arranged for the service vehicle up to 7,5 metric tons (with the possibility to increase

transport load up to 12,5 metric tons or more).

10.7 Architectural buildings Going from structural to architectonical applications, a significant aluminium building is the former Aluminium

Centrum in Utrecht (The Netherlands), designed by Micha de Haas, which main body is supported by a “forest” of

tubular columns, part in the water and part in the bank side (Fig. 10.36).

10.8 Other applications

Aluminium proved to be a suitable material also for other special applications such rear underrun protection

components for mobile cranes and heavy trucks (Fig. 10.37, 10.38 and 10.39), whose main purpose is to limit as much

as possible the intrusion of cars in case of road accidents. Also in this case, the selection of an aluminium beam was

the best cost-technical-weight compromise when compared to other existing solutions. The beam weight could be

significantly reduced in comparison to a steel beam solution, while benefitting at the same time from optimal corrosion

protection and functional integration.



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Figure 10.1 The lattice space structure of the Interamerican Exhibition Center of San Paulo (Brazil): erection phases.

Figure 10.2 The Conference Centre of Rio de Janeiro (Brazil).

Figure 10.3. Sport Hall of Quito (Ecuador).

Figure 10.4: Hatogrande (left) and Guymaral (right) Country Clubs in Bogotá (Colombia)



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Figure 10.5 Dome of Discovery (London)

Figure 10.6: Palais des sports (Paris)



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Figure 10.7: Geodetic domes for industrial applications

a) South Pole scientific station b) University of Connecticut (USA)

c) Bell County Arena (Temple, Texas, USA)

Figure 10.8: Tem-cor geodetic domes.

Figures 10.9: The “Spruce Goose” dome in Long Beach (USA): erection phases

d) Baylor University Ferrell Events Centre (Waco,

Texas, USA)



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Figure 10.10: The geodetic dome in the “Mercati Traianei” Museum in Rome (Italy)

Figure 10.11: Aluminium domes for coal storage plants



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Figure 10.12: The ENEL geodetic domes in Torrevaldaliga (Rome, Italy)

Figure 10.13: Traffic sign portal



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Figure 10.14: Electrical transmission tower

Figure 10.15: The ENEL antennas tower (Naples, Italy)



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Figure 10.16: The “Information” tower (Naples, Italy)

Figure 10.17: The sewage plant pool of Po-Sangone (Torino, Italy)



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Figure 10.18: Off-shore platform

Figure 10.19: Prefabricated unit for off-shore platform



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Figure 10.20: Helideck Figure 10.21: Complete crew quarter on off-shore platform

Figure 10.22: The “Arvida” bridge in Quebec (Canada).



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Figure 10.23: Motorway bridge crossing a canal in Amsterdam (The Netherlands)

Figures 10.24 Pedestrian bridges



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Figure 10.25 The opening bridge of the Aberdeen harbour (Scotland) Figure 10.26 A simple moving footbridge (DE)

Figure 10.27 Floating bridge



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Figures 10.28 different types of military bridges

Figure 10.29 Extrusion plates for bridge decks



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Figure 10.30 The Montmerle bridge on the Saône river (France)

Figure 10.31 The Trevoux Bridge on the Saône river (France)



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Figure 10.32: The Groslée bridge on the Rhône river (France)

Figures 10.33: The “Real Ferdinando” bridge on the Garigliano river (Italy).



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Figures 10.34 and 10.35: Aluminium Bridges (toolbridge© by Bitschnau)

Figure 10.36: The former “Aluminium Centrum” in Utrecht (The Netherland).



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Figures 10.37, 10.38 and 10.39: Rear underrun protection component, car intrusion test, aluminium beams (pictures by Hydro)



98

Terms and definitions ageing treatment of a metal aiming at a change in its properties by precipitation of intermetallic phases from supersaturated solid solution annealing thermal treatment to soften metal by reduction or removal of strain hardening resulting from cold working and/or by coalescing precipitates from solid solution buckling sudden change in shape of a structural component under load (e.g. the bowing of a column subjected to compression forces) casting product at or near finished shape, formed by solidification of the metal in a mould or a die cold working forming of solid metal without preheating (also said work-hardening or strain hardening) extrusion ingot ingot, intended and suitable for extruding, typically with a solid, circular cross-section but sometimes with a central hollow or a flattened cross-section extrusion billet extrusion ingot cut to length Heat Affected Zone (HAZ) a non-melted area of metal that has undergone changes in material properties as a result of being exposed to high temperatures heat treatable alloy alloy which can be strengthened by a suitable thermal treatment hot working forming of solid metal after pre-heating formability relative ease with which a metal can be formed by rolling, extruding, drawing, deep drawing, forging, etc. lattice imperfection imperfection in the regular geometrical arrangement of the atoms in a solid lacquering process that involves a surface application that increases the strength and tear resistance of the aluminium as well as the gloss and adherence of other coatings EN 12258-1 says: coating with a formulation based on a dissolved material which forms a transparent layer primarily after drying by evaporation of the solvent non-heat-treatable alloy

alloy which is not strengthened by thermal treatment (only strengthened by hot or cold working).



99

quenching

cooling a metal from an elevated temperature by contact with a solid, a liquid or a gas, at a rate rapid enough to retain most or all of the soluble constituents in solid solution

solution heat-treatment heating an alloy at a suitable temperature for a sufficient time to allow one or more soluble constituents to enter into solid solution, where they are retained in a supersaturated state after quenching (rapid cooling) strain-hardening modification of a metal structure, by cold working, resulting in an increase in strength and hardness, generally with loss of ductility temper

condition of the metal produced by mechanical and/or thermal processing, typically characterized by a certain

structure and specified properties



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Standards & Normative references EN 1090-1:2009+A1:2011: Execution of steel structures and aluminium structures. Requirements for conformity

assessment of structural components

EN 1090-3:2019: Execution of steel structures and aluminium structures. Technical requirements for aluminium

structures

EN 1090-5:2017: Execution of steel structures and aluminium structures. Technical requirements for cold-formed

structural aluminium elements and cold-formed structures for roof, ceiling, floor and wall applications

EN 12020-1: Aluminium and aluminium alloys - Extruded precision profiles in alloys EN AW-6060 and EN AW-6063 –

Part 1: Technical conditions for inspection and delivery

EN 12020-2: Aluminium and aluminium alloys - Extruded precision profiles in alloys EN AW-6060 and EN AW-6063 -

Part 2: Tolerances on dimensions and form

EN 12258-1, Aluminium and aluminium alloys - Terms and definitions - Part 1: General terms

EN 15088, Aluminium and aluminium alloys - Structural products for construction works

EN 1780-1, Aluminium and aluminium alloys - Designation of alloyed aluminium ingots for re-melting, master alloys

and castings - Part 1: Numerical designation system

EN 1780-2, Aluminium and aluminium alloys - Designation of alloyed aluminium ingots for remelting, master alloys and

castings - Part 2: Chemical symbol-based designation system

EN 1780-3, Aluminium and aluminium alloys - Designation of alloyed aluminium ingots for re-melting, master alloys

and castings - Part 3: Writing rules for chemical composition

EN 1990, Eurocode 0: Basis of structural design

EN 1999, Eurocode 9: Design of aluminium structures

EN 1999-1-1: General structural rules

EN 1999-1-2: Structural fire design

EN 1999-1-3: Structures susceptible to fatigue

EN 1999-1-4: Cold-formed structural sheeting

EN 1999-1-5: Shell structures

EN 515: Aluminium and aluminium alloys - Wrought products - Temper designations

EN 573-1: Aluminium and aluminium alloys - Chemical composition and form of wrought products - Part 1: Numerical

designation system

EN 573-2: Aluminium and aluminium alloys - Chemical composition and form of wrought products - Part 2: Chemical

symbol-based designation system



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EN 573-3: Aluminium and aluminium alloys - Chemical composition and form of wrought products - Part 3: Chemical

composition and form of products

EN 755: Aluminium and aluminium alloys. Extruded rod/bar, tube and profiles

EN 755-1: Aluminium and aluminium alloys- Extruded rod/bar, tube and profiles – Part 1: Technical conditions for inspection and delivery EN 755-2: Aluminium and aluminium alloys- Extruded rod/bar, tube and profiles – Part 2: Mechanical properties EN 755-3/9: Aluminium and aluminium alloys- Extruded rod/bar, tube and profiles – Parts 3 to 9: Tolerances on dimensions and form Eurocodes, Joint Research Centre – online available at https://eurocodes.jrc.ec.europa.eu/

Regulation (EU) No 305/2011 on Construction Products, online available at https://eur-lex.europa.eu/legal-

content/EN/ALL/?uri=celex:32011R0305

https://eurocodes.jrc.ec.europa.eu/

https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=celex:32011R0305

https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=celex:32011R0305



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Basic references GITTER, R. (2006) Aluminium Materials for structural engineering - Essential properties and selection of Materials; SEI

- Structural Engineering International; Vol.16, Number 4; November 2006.

HӦGLUND, T.; TINDALL, P. (2012) Designers' Guide to Eurocode 9: Design of Aluminium Structures EN 1999-1-1 and -

1-4, ICE Publishing, Thomas Telford Limited, 2012

MAZZOLANI, F.M. (1995) Aluminium Alloy Structures (second edition), E&FN SPON, Chapman & Hall, 2nd ed., 1995.

Other references

European Aluminium, Aluminium in commercial vehicles – online available at https://www.european-

aluminium.eu/media/1295/aluminium-in-commercial-vehicle_en.pdf

European Aluminium, Sustainability of aluminium in buildings – online available at https://www.european-

aluminium.eu/media/1311/en-sustainability-of-aluminium-in-buildings.pdf

MAZZOLANI, F.M. (1985) A new aluminium crane bridge for sewage treatment plants, Proceedings of the 3rd International Conference on Aluminium Weldments, Munich, 1985

MAZZOLANI, F.M. (2001) The use of aluminium in the restoration of the “Real Ferdinando” bridge on the Garigliano river, Festschrift zu Ehren Von Prof. Dr. Ing. Gunther Valtinat, Herausgegeben von Jurgen Priebe und Ulrike Eberwien, Druck: General An-zeiger, Rhauderfehn, 2001.

MAZZOLANI. F.M.; MAZZOLANI, S. M. and MANDARA, A. (2005) The use of aluminium structures in the restoration project of Mercati Traianei in Rome, Proceedings of the 5th International Congress on Restoration of Architectural Heritage, Florence, 13-15 October 2005

MAZZOLANI, F.M. (2006) Structural applications of Aluminium in Civil Engineering, Structural Engineering International, vol.16, n.4, pp.280-285, November 2006

MAZZOLANI, F.M. (2010) Two twin aluminium domes of the ENEL plant in Civitavecchia (Italy), Proceedings of the International Aluminium Conference (INALCO): “New frontiers in Light Metals”, Eindhoven, 23-25 June 2010

https://www.european-aluminium.eu/media/1295/aluminium-in-commercial-vehicle_en.pdf

https://www.european-aluminium.eu/media/1295/aluminium-in-commercial-vehicle_en.pdf

https://www.european-aluminium.eu/media/1311/en-sustainability-of-aluminium-in-buildings.pdf

https://www.european-aluminium.eu/media/1311/en-sustainability-of-aluminium-in-buildings.pdf